base/trace_event/trace_event.h

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_TRACE_EVENT_TRACE_EVENT_H_
#define BASE_TRACE_EVENT_TRACE_EVENT_H_

// This header file defines implementation details of how the trace macros in
// trace_event_common.h collect and store trace events. Anything not
// implementation-specific should go in trace_event_common.h instead of here.

#include <stddef.h>
#include <stdint.h>

#include <string>

#include "base/atomicops.h"
#include "base/macros.h"
#include "base/time/time.h"
#include "base/trace_event/common/trace_event_common.h"
#include "base/trace_event/heap_profiler.h"
#include "base/trace_event/trace_event_system_stats_monitor.h"
#include "base/trace_event/trace_log.h"
#include "build/build_config.h"

// By default, const char* argument values are assumed to have long-lived scope
// and will not be copied. Use this macro to force a const char* to be copied.
#define TRACE_STR_COPY(str) \
    trace_event_internal::TraceStringWithCopy(str)

// By default, uint64_t ID argument values are not mangled with the Process ID
// in TRACE_EVENT_ASYNC macros. Use this macro to force Process ID mangling.
#define TRACE_ID_MANGLE(id) \
    trace_event_internal::TraceID::ForceMangle(id)

// By default, pointers are mangled with the Process ID in TRACE_EVENT_ASYNC
// macros. Use this macro to prevent Process ID mangling.
#define TRACE_ID_DONT_MANGLE(id) \
    trace_event_internal::TraceID::DontMangle(id)

// By default, trace IDs are eventually converted to a single 64-bit number. Use
// this macro to add a scope string.
#define TRACE_ID_WITH_SCOPE(scope, id) \
    trace_event_internal::TraceID::WithScope(scope, id)

// Sets the current sample state to the given category and name (both must be
// constant strings). These states are intended for a sampling profiler.
// Implementation note: we store category and name together because we don't
// want the inconsistency/expense of storing two pointers.
// |thread_bucket| is [0..2] and is used to statically isolate samples in one
// thread from others.
#define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET( \
    bucket_number, category, name)                 \
        trace_event_internal::                     \
        TraceEventSamplingStateScope<bucket_number>::Set(category "\0" name)

// Returns a current sampling state of the given bucket.
#define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
    trace_event_internal::TraceEventSamplingStateScope<bucket_number>::Current()

// Creates a scope of a sampling state of the given bucket.
//
// {  // The sampling state is set within this scope.
//    TRACE_EVENT_SAMPLING_STATE_SCOPE_FOR_BUCKET(0, "category", "name");
//    ...;
// }
#define TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(                   \
    bucket_number, category, name)                                      \
    trace_event_internal::TraceEventSamplingStateScope<bucket_number>   \
        traceEventSamplingScope(category "\0" name);

#define TRACE_EVENT_API_CURRENT_THREAD_ID \
  static_cast<int>(base::PlatformThread::CurrentId())

#define INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE() \
  UNLIKELY(*INTERNAL_TRACE_EVENT_UID(category_group_enabled) &           \
           (base::trace_event::TraceLog::ENABLED_FOR_RECORDING |         \
            base::trace_event::TraceLog::ENABLED_FOR_EVENT_CALLBACK |    \
            base::trace_event::TraceLog::ENABLED_FOR_ETW_EXPORT))

////////////////////////////////////////////////////////////////////////////////
// Implementation specific tracing API definitions.

// Get a pointer to the enabled state of the given trace category. Only
// long-lived literal strings should be given as the category group. The
// returned pointer can be held permanently in a local static for example. If
// the unsigned char is non-zero, tracing is enabled. If tracing is enabled,
// TRACE_EVENT_API_ADD_TRACE_EVENT can be called. It's OK if tracing is disabled
// between the load of the tracing state and the call to
// TRACE_EVENT_API_ADD_TRACE_EVENT, because this flag only provides an early out
// for best performance when tracing is disabled.
// const unsigned char*
//     TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(const char* category_group)
#define TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED \
    base::trace_event::TraceLog::GetCategoryGroupEnabled

// Get the number of times traces have been recorded. This is used to implement
// the TRACE_EVENT_IS_NEW_TRACE facility.
// unsigned int TRACE_EVENT_API_GET_NUM_TRACES_RECORDED()
#define TRACE_EVENT_API_GET_NUM_TRACES_RECORDED \
    base::trace_event::TraceLog::GetInstance()->GetNumTracesRecorded

// Add a trace event to the platform tracing system.
// base::trace_event::TraceEventHandle TRACE_EVENT_API_ADD_TRACE_EVENT(
//                    char phase,
//                    const unsigned char* category_group_enabled,
//                    const char* name,
//                    const char* scope,
//                    unsigned long long id,
//                    int num_args,
//                    const char** arg_names,
//                    const unsigned char* arg_types,
//                    const unsigned long long* arg_values,
//                    std::unique_ptr<ConvertableToTraceFormat>*
//                    convertable_values,
//                    unsigned int flags)
#define TRACE_EVENT_API_ADD_TRACE_EVENT \
    base::trace_event::TraceLog::GetInstance()->AddTraceEvent

// Add a trace event to the platform tracing system.
// base::trace_event::TraceEventHandle
// TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_BIND_ID(
//                    char phase,
//                    const unsigned char* category_group_enabled,
//                    const char* name,
//                    const char* scope,
//                    unsigned long long id,
//                    unsigned long long bind_id,
//                    int num_args,
//                    const char** arg_names,
//                    const unsigned char* arg_types,
//                    const unsigned long long* arg_values,
//                    std::unique_ptr<ConvertableToTraceFormat>*
//                    convertable_values,
//                    unsigned int flags)
#define TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_BIND_ID \
  base::trace_event::TraceLog::GetInstance()->AddTraceEventWithBindId

// Add a trace event to the platform tracing system overriding the pid.
// The resulting event will have tid = pid == (process_id passed here).
// base::trace_event::TraceEventHandle
// TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_PROCESS_ID(
//                    char phase,
//                    const unsigned char* category_group_enabled,
//                    const char* name,
//                    const char* scope,
//                    unsigned long long id,
//                    int process_id,
//                    int num_args,
//                    const char** arg_names,
//                    const unsigned char* arg_types,
//                    const unsigned long long* arg_values,
//                    std::unique_ptr<ConvertableToTraceFormat>*
//                    convertable_values,
//                    unsigned int flags)
#define TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_PROCESS_ID \
  base::trace_event::TraceLog::GetInstance()->AddTraceEventWithProcessId

// Add a trace event to the platform tracing system.
// base::trace_event::TraceEventHandle
// TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_TIMESTAMP(
//                    char phase,
//                    const unsigned char* category_group_enabled,
//                    const char* name,
//                    const char* scope,
//                    unsigned long long id,
//                    int thread_id,
//                    const TimeTicks& timestamp,
//                    int num_args,
//                    const char** arg_names,
//                    const unsigned char* arg_types,
//                    const unsigned long long* arg_values,
//                    std::unique_ptr<ConvertableToTraceFormat>*
//                    convertable_values,
//                    unsigned int flags)
#define TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP \
    base::trace_event::TraceLog::GetInstance() \
      ->AddTraceEventWithThreadIdAndTimestamp

// Set the duration field of a COMPLETE trace event.
// void TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
//     const unsigned char* category_group_enabled,
//     const char* name,
//     base::trace_event::TraceEventHandle id)
#define TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION \
    base::trace_event::TraceLog::GetInstance()->UpdateTraceEventDuration

// Adds a metadata event to the trace log. The |AppendValueAsTraceFormat| method
// on the convertable value will be called at flush time.
// TRACE_EVENT_API_ADD_METADATA_EVENT(
//     const unsigned char* category_group_enabled,
//     const char* event_name,
//     const char* arg_name,
//     std::unique_ptr<ConvertableToTraceFormat> arg_value)
#define TRACE_EVENT_API_ADD_METADATA_EVENT \
    trace_event_internal::AddMetadataEvent

// Defines atomic operations used internally by the tracing system.
#define TRACE_EVENT_API_ATOMIC_WORD base::subtle::AtomicWord
#define TRACE_EVENT_API_ATOMIC_LOAD(var) base::subtle::NoBarrier_Load(&(var))
#define TRACE_EVENT_API_ATOMIC_STORE(var, value) \
    base::subtle::NoBarrier_Store(&(var), (value))

// Defines visibility for classes in trace_event.h
#define TRACE_EVENT_API_CLASS_EXPORT BASE_EXPORT

// The thread buckets for the sampling profiler.
TRACE_EVENT_API_CLASS_EXPORT extern \
    TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];

#define TRACE_EVENT_API_THREAD_BUCKET(thread_bucket)                           \
    g_trace_state[thread_bucket]

////////////////////////////////////////////////////////////////////////////////

// Implementation detail: trace event macros create temporary variables
// to keep instrumentation overhead low. These macros give each temporary
// variable a unique name based on the line number to prevent name collisions.
#define INTERNAL_TRACE_EVENT_UID3(a,b) \
    trace_event_unique_##a##b
#define INTERNAL_TRACE_EVENT_UID2(a,b) \
    INTERNAL_TRACE_EVENT_UID3(a,b)
#define INTERNAL_TRACE_EVENT_UID(name_prefix) \
    INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)

// Implementation detail: internal macro to create static category.
// No barriers are needed, because this code is designed to operate safely
// even when the unsigned char* points to garbage data (which may be the case
// on processors without cache coherency).
#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES( \
    category_group, atomic, category_group_enabled) \
    category_group_enabled = \
        reinterpret_cast<const unsigned char*>(TRACE_EVENT_API_ATOMIC_LOAD( \
            atomic)); \
    if (UNLIKELY(!category_group_enabled)) { \
      category_group_enabled = \
          TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group); \
      TRACE_EVENT_API_ATOMIC_STORE(atomic, \
          reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>( \
              category_group_enabled)); \
    }

#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group) \
    static TRACE_EVENT_API_ATOMIC_WORD INTERNAL_TRACE_EVENT_UID(atomic) = 0; \
    const unsigned char* INTERNAL_TRACE_EVENT_UID(category_group_enabled); \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES(category_group, \
        INTERNAL_TRACE_EVENT_UID(atomic), \
        INTERNAL_TRACE_EVENT_UID(category_group_enabled));

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#define INTERNAL_TRACE_EVENT_ADD(phase, category_group, name, flags, ...) \
    do { \
      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
      if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
        trace_event_internal::AddTraceEvent( \
            phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
            trace_event_internal::kGlobalScope, trace_event_internal::kNoId, \
            flags, trace_event_internal::kNoId, ##__VA_ARGS__); \
      } \
    } while (0)

// Implementation detail: internal macro to create static category and add begin
// event if the category is enabled. Also adds the end event when the scope
// ends.
#define INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name, ...) \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
    trace_event_internal::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer); \
    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
      base::trace_event::TraceEventHandle h = \
          trace_event_internal::AddTraceEvent( \
              TRACE_EVENT_PHASE_COMPLETE, \
              INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
              trace_event_internal::kGlobalScope, trace_event_internal::kNoId, \
              TRACE_EVENT_FLAG_NONE, trace_event_internal::kNoId, \
              ##__VA_ARGS__); \
      INTERNAL_TRACE_EVENT_UID(tracer).Initialize( \
          INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, h); \
    }

#define INTERNAL_TRACE_EVENT_ADD_SCOPED_WITH_FLOW( \
    category_group, name, bind_id, flow_flags, ...) \
  INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
  trace_event_internal::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer); \
  if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
    unsigned int trace_event_flags = flow_flags; \
    trace_event_internal::TraceID trace_event_bind_id(bind_id, \
                                                      &trace_event_flags); \
    base::trace_event::TraceEventHandle h = \
        trace_event_internal::AddTraceEvent( \
            TRACE_EVENT_PHASE_COMPLETE, \
            INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
            trace_event_internal::kGlobalScope, trace_event_internal::kNoId, \
            trace_event_flags, trace_event_bind_id.raw_id(), ##__VA_ARGS__); \
    INTERNAL_TRACE_EVENT_UID(tracer).Initialize( \
        INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, h); \
  }

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category_group, name, id, \
                                         flags, ...) \
    do { \
      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
      if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
        unsigned int trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID; \
        trace_event_internal::TraceID trace_event_trace_id( \
            id, &trace_event_flags); \
        trace_event_internal::AddTraceEvent( \
            phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
            name, trace_event_trace_id.scope(), trace_event_trace_id.raw_id(), \
            trace_event_flags, trace_event_internal::kNoId, ##__VA_ARGS__); \
      } \
    } while (0)

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#define INTERNAL_TRACE_EVENT_ADD_WITH_TIMESTAMP(phase, category_group, name, \
                                                timestamp, flags, ...)       \
  do {                                                                       \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                  \
    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) {  \
      trace_event_internal::AddTraceEventWithThreadIdAndTimestamp(           \
          phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,     \
          trace_event_internal::kGlobalScope, trace_event_internal::kNoId,   \
          TRACE_EVENT_API_CURRENT_THREAD_ID,                                 \
          base::TimeTicks::FromInternalValue(timestamp),                     \
          flags | TRACE_EVENT_FLAG_EXPLICIT_TIMESTAMP,                       \
          trace_event_internal::kNoId, ##__VA_ARGS__);                       \
    }                                                                        \
  } while (0)

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#define INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(                   \
    phase, category_group, name, id, thread_id, timestamp, flags, ...)        \
  do {                                                                        \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                   \
    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) {   \
      unsigned int trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID;       \
      trace_event_internal::TraceID trace_event_trace_id(id,                  \
                                                         &trace_event_flags); \
      trace_event_internal::AddTraceEventWithThreadIdAndTimestamp(            \
          phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,      \
          trace_event_trace_id.scope(), trace_event_trace_id.raw_id(),        \
          thread_id, base::TimeTicks::FromInternalValue(timestamp),           \
          trace_event_flags | TRACE_EVENT_FLAG_EXPLICIT_TIMESTAMP,            \
          trace_event_internal::kNoId, ##__VA_ARGS__);                        \
    }                                                                         \
  } while (0)

// Implementation detail: internal macro to create static category and add
// metadata event if the category is enabled.
#define INTERNAL_TRACE_EVENT_METADATA_ADD(category_group, name, ...)        \
  do {                                                                      \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group);                 \
    if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
      TRACE_EVENT_API_ADD_METADATA_EVENT(                                   \
          INTERNAL_TRACE_EVENT_UID(category_group_enabled), name,           \
          ##__VA_ARGS__);                                                   \
    }                                                                       \
  } while (0)

// Implementation detail: internal macro to enter and leave a
// context based on the current scope.
#define INTERNAL_TRACE_EVENT_SCOPED_CONTEXT(category_group, name, context) \
  struct INTERNAL_TRACE_EVENT_UID(ScopedContext) {                         \
   public:                                                                 \
    INTERNAL_TRACE_EVENT_UID(ScopedContext)(uint64_t cid) : cid_(cid) {    \
      TRACE_EVENT_ENTER_CONTEXT(category_group, name, cid_);               \
    }                                                                      \
    ~INTERNAL_TRACE_EVENT_UID(ScopedContext)() {                           \
      TRACE_EVENT_LEAVE_CONTEXT(category_group, name, cid_);               \
    }                                                                      \
                                                                           \
   private:                                                                \
    uint64_t cid_;                                                         \
    /* Local class friendly DISALLOW_COPY_AND_ASSIGN */                    \
    INTERNAL_TRACE_EVENT_UID(ScopedContext)                                \
    (const INTERNAL_TRACE_EVENT_UID(ScopedContext)&) {};                   \
    void operator=(const INTERNAL_TRACE_EVENT_UID(ScopedContext)&) {};     \
  };                                                                       \
  INTERNAL_TRACE_EVENT_UID(ScopedContext)                                  \
  INTERNAL_TRACE_EVENT_UID(scoped_context)(context.raw_id());

// Implementation detail: internal macro to trace a task execution with the
// location where it was posted from.
#define INTERNAL_TRACE_TASK_EXECUTION(run_function, task)                 \
  TRACE_EVENT2("toplevel", run_function, "src_file",                      \
               (task).posted_from.file_name(), "src_func",                \
               (task).posted_from.function_name());                       \
  TRACE_HEAP_PROFILER_API_SCOPED_TASK_EXECUTION INTERNAL_TRACE_EVENT_UID( \
      task_event)((task).posted_from.file_name());

namespace trace_event_internal {

// Specify these values when the corresponding argument of AddTraceEvent is not
// used.
const int kZeroNumArgs = 0;
const std::nullptr_t kGlobalScope = nullptr;
const unsigned long long kNoId = 0;

// TraceID encapsulates an ID that can either be an integer or pointer. Pointers
// are by default mangled with the Process ID so that they are unlikely to
// collide when the same pointer is used on different processes.
class TraceID {
 public:
  class WithScope {
   public:
    WithScope(const char* scope, unsigned long long raw_id)
        : scope_(scope), raw_id_(raw_id) {}
    unsigned long long raw_id() const { return raw_id_; }
    const char* scope() const { return scope_; }
   private:
    const char* scope_ = nullptr;
    unsigned long long raw_id_;
  };

  class DontMangle {
   public:
    explicit DontMangle(const void* raw_id)
        : raw_id_(static_cast<unsigned long long>(
              reinterpret_cast<uintptr_t>(raw_id))) {}
    explicit DontMangle(unsigned long long raw_id) : raw_id_(raw_id) {}
    explicit DontMangle(unsigned long raw_id) : raw_id_(raw_id) {}
    explicit DontMangle(unsigned int raw_id) : raw_id_(raw_id) {}
    explicit DontMangle(unsigned short raw_id) : raw_id_(raw_id) {}
    explicit DontMangle(unsigned char raw_id) : raw_id_(raw_id) {}
    explicit DontMangle(long long raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit DontMangle(long raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit DontMangle(int raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit DontMangle(short raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit DontMangle(signed char raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit DontMangle(WithScope scoped_id)
        : scope_(scoped_id.scope()), raw_id_(scoped_id.raw_id()) {}
    const char* scope() const { return scope_; }
    unsigned long long raw_id() const { return raw_id_; }
   private:
    const char* scope_ = nullptr;
    unsigned long long raw_id_;
  };

  class ForceMangle {
   public:
    explicit ForceMangle(unsigned long long raw_id) : raw_id_(raw_id) {}
    explicit ForceMangle(unsigned long raw_id) : raw_id_(raw_id) {}
    explicit ForceMangle(unsigned int raw_id) : raw_id_(raw_id) {}
    explicit ForceMangle(unsigned short raw_id) : raw_id_(raw_id) {}
    explicit ForceMangle(unsigned char raw_id) : raw_id_(raw_id) {}
    explicit ForceMangle(long long raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit ForceMangle(long raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit ForceMangle(int raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit ForceMangle(short raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    explicit ForceMangle(signed char raw_id)
        : raw_id_(static_cast<unsigned long long>(raw_id)) {}
    unsigned long long raw_id() const { return raw_id_; }
   private:
    unsigned long long raw_id_;
  };
  TraceID(const void* raw_id, unsigned int* flags)
      : raw_id_(static_cast<unsigned long long>(
                reinterpret_cast<uintptr_t>(raw_id))) {
    *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
  }
  TraceID(ForceMangle raw_id, unsigned int* flags) : raw_id_(raw_id.raw_id()) {
    *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
  }
  TraceID(DontMangle maybe_scoped_id, unsigned int* /*flags*/)
      : scope_(maybe_scoped_id.scope()), raw_id_(maybe_scoped_id.raw_id()) {}
  TraceID(unsigned long long raw_id, unsigned int* flags) : raw_id_(raw_id) {
    (void)flags;
  }
  TraceID(unsigned long raw_id, unsigned int* flags) : raw_id_(raw_id) {
    (void)flags;
  }
  TraceID(unsigned int raw_id, unsigned int* flags) : raw_id_(raw_id) {
    (void)flags;
  }
  TraceID(unsigned short raw_id, unsigned int* flags) : raw_id_(raw_id) {
    (void)flags;
  }
  TraceID(unsigned char raw_id, unsigned int* flags) : raw_id_(raw_id) {
    (void)flags;
  }
  TraceID(long long raw_id, unsigned int* flags)
      : raw_id_(static_cast<unsigned long long>(raw_id)) { (void)flags; }
  TraceID(long raw_id, unsigned int* flags)
      : raw_id_(static_cast<unsigned long long>(raw_id)) { (void)flags; }
  TraceID(int raw_id, unsigned int* flags)
      : raw_id_(static_cast<unsigned long long>(raw_id)) { (void)flags; }
  TraceID(short raw_id, unsigned int* flags)
      : raw_id_(static_cast<unsigned long long>(raw_id)) { (void)flags; }
  TraceID(signed char raw_id, unsigned int* flags)
      : raw_id_(static_cast<unsigned long long>(raw_id)) { (void)flags; }
  TraceID(WithScope scoped_id, unsigned int* /*flags*/)
      : scope_(scoped_id.scope()), raw_id_(scoped_id.raw_id()) {}

  unsigned long long raw_id() const { return raw_id_; }
  const char* scope() const { return scope_; }

 private:
  const char* scope_ = nullptr;
  unsigned long long raw_id_;
};

// Simple union to store various types as unsigned long long.
union TraceValueUnion {
  bool as_bool;
  unsigned long long as_uint;
  long long as_int;
  double as_double;
  const void* as_pointer;
  const char* as_string;
};

// Simple container for const char* that should be copied instead of retained.
class TraceStringWithCopy {
 public:
  explicit TraceStringWithCopy(const char* str) : str_(str) {}
  const char* str() const { return str_; }
 private:
  const char* str_;
};

// Define SetTraceValue for each allowed type. It stores the type and
// value in the return arguments. This allows this API to avoid declaring any
// structures so that it is portable to third_party libraries.
#define INTERNAL_DECLARE_SET_TRACE_VALUE(actual_type, \
                                         arg_expression, \
                                         union_member, \
                                         value_type_id) \
    static inline void SetTraceValue( \
        actual_type arg, \
        unsigned char* type, \
        unsigned long long* value) { \
      TraceValueUnion type_value; \
      type_value.union_member = arg_expression; \
      *type = value_type_id; \
      *value = type_value.as_uint; \
    }
// Simpler form for int types that can be safely casted.
#define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actual_type, \
                                             value_type_id) \
    static inline void SetTraceValue( \
        actual_type arg, \
        unsigned char* type, \
        unsigned long long* value) { \
      *type = value_type_id; \
      *value = static_cast<unsigned long long>(arg); \
    }

INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned long long, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned long, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned int, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned short, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long long, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(short, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE(bool, arg, as_bool, TRACE_VALUE_TYPE_BOOL)
INTERNAL_DECLARE_SET_TRACE_VALUE(double, arg, as_double,
                                 TRACE_VALUE_TYPE_DOUBLE)
INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, arg, as_pointer,
                                 TRACE_VALUE_TYPE_POINTER)
INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, arg, as_string,
                                 TRACE_VALUE_TYPE_STRING)
INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, arg.str(),
                                 as_string, TRACE_VALUE_TYPE_COPY_STRING)

#undef INTERNAL_DECLARE_SET_TRACE_VALUE
#undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT

// std::string version of SetTraceValue so that trace arguments can be strings.
static inline void SetTraceValue(const std::string& arg,
                                 unsigned char* type,
                                 unsigned long long* value) {
  TraceValueUnion type_value;
  type_value.as_string = arg.c_str();
  *type = TRACE_VALUE_TYPE_COPY_STRING;
  *value = type_value.as_uint;
}

// base::Time, base::TimeTicks, etc. versions of SetTraceValue to make it easier
// to trace these types.
static inline void SetTraceValue(const base::Time arg,
                                 unsigned char* type,
                                 unsigned long long* value) {
  *type = TRACE_VALUE_TYPE_INT;
  *value = arg.ToInternalValue();
}

static inline void SetTraceValue(const base::TimeTicks arg,
                                 unsigned char* type,
                                 unsigned long long* value) {
  *type = TRACE_VALUE_TYPE_INT;
  *value = arg.ToInternalValue();
}

static inline void SetTraceValue(const base::ThreadTicks arg,
                                 unsigned char* type,
                                 unsigned long long* value) {
  *type = TRACE_VALUE_TYPE_INT;
  *value = arg.ToInternalValue();
}

// These AddTraceEvent and AddTraceEventWithThreadIdAndTimestamp template
// functions are defined here instead of in the macro, because the arg_values
// could be temporary objects, such as std::string. In order to store
// pointers to the internal c_str and pass through to the tracing API,
// the arg_values must live throughout these procedures.

template <class ARG1_CONVERTABLE_TYPE>
static inline base::trace_event::TraceEventHandle
AddTraceEventWithThreadIdAndTimestamp(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    int thread_id,
    const base::TimeTicks& timestamp,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    std::unique_ptr<ARG1_CONVERTABLE_TYPE> arg1_val) {
  const int num_args = 1;
  unsigned char arg_types[1] = { TRACE_VALUE_TYPE_CONVERTABLE };
  std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
      convertable_values[1] = {std::move(arg1_val)};
  return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
      phase, category_group_enabled, name, scope, id, bind_id, thread_id,
      timestamp, num_args, &arg1_name, arg_types, NULL, convertable_values,
      flags);
}

template <class ARG1_TYPE, class ARG2_CONVERTABLE_TYPE>
static inline base::trace_event::TraceEventHandle
AddTraceEventWithThreadIdAndTimestamp(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    int thread_id,
    const base::TimeTicks& timestamp,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    const ARG1_TYPE& arg1_val,
    const char* arg2_name,
    std::unique_ptr<ARG2_CONVERTABLE_TYPE> arg2_val) {
  const int num_args = 2;
  const char* arg_names[2] = { arg1_name, arg2_name };

  unsigned char arg_types[2];
  unsigned long long arg_values[2];
  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
  arg_types[1] = TRACE_VALUE_TYPE_CONVERTABLE;
  std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
      convertable_values[2] = {nullptr, std::move(arg2_val)};
  return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
      phase, category_group_enabled, name, scope, id, bind_id, thread_id,
      timestamp, num_args, arg_names, arg_types, arg_values, convertable_values,
      flags);
}

template <class ARG1_CONVERTABLE_TYPE, class ARG2_TYPE>
static inline base::trace_event::TraceEventHandle
AddTraceEventWithThreadIdAndTimestamp(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    int thread_id,
    const base::TimeTicks& timestamp,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    std::unique_ptr<ARG1_CONVERTABLE_TYPE> arg1_val,
    const char* arg2_name,
    const ARG2_TYPE& arg2_val) {
  const int num_args = 2;
  const char* arg_names[2] = { arg1_name, arg2_name };

  unsigned char arg_types[2];
  unsigned long long arg_values[2];
  arg_types[0] = TRACE_VALUE_TYPE_CONVERTABLE;
  arg_values[0] = 0;
  SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
  std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
      convertable_values[2] = {std::move(arg1_val), nullptr};
  return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
      phase, category_group_enabled, name, scope, id, bind_id, thread_id,
      timestamp, num_args, arg_names, arg_types, arg_values, convertable_values,
      flags);
}

template <class ARG1_CONVERTABLE_TYPE, class ARG2_CONVERTABLE_TYPE>
static inline base::trace_event::TraceEventHandle
AddTraceEventWithThreadIdAndTimestamp(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    int thread_id,
    const base::TimeTicks& timestamp,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    std::unique_ptr<ARG1_CONVERTABLE_TYPE> arg1_val,
    const char* arg2_name,
    std::unique_ptr<ARG2_CONVERTABLE_TYPE> arg2_val) {
  const int num_args = 2;
  const char* arg_names[2] = { arg1_name, arg2_name };
  unsigned char arg_types[2] =
      { TRACE_VALUE_TYPE_CONVERTABLE, TRACE_VALUE_TYPE_CONVERTABLE };
  std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
      convertable_values[2] = {std::move(arg1_val), std::move(arg2_val)};
  return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
      phase, category_group_enabled, name, scope, id, bind_id, thread_id,
      timestamp, num_args, arg_names, arg_types, NULL, convertable_values,
      flags);
}

static inline base::trace_event::TraceEventHandle
AddTraceEventWithThreadIdAndTimestamp(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    int thread_id,
    const base::TimeTicks& timestamp,
    unsigned int flags,
    unsigned long long bind_id) {
  return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
      phase, category_group_enabled, name, scope, id, bind_id, thread_id,
      timestamp, kZeroNumArgs, NULL, NULL, NULL, NULL, flags);
}

static inline base::trace_event::TraceEventHandle AddTraceEvent(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    unsigned int flags,
    unsigned long long bind_id) {
  const int thread_id = static_cast<int>(base::PlatformThread::CurrentId());
  const base::TimeTicks now = base::TimeTicks::Now();
  return AddTraceEventWithThreadIdAndTimestamp(
      phase, category_group_enabled, name, scope, id, thread_id, now, flags,
      bind_id);
}

template<class ARG1_TYPE>
static inline base::trace_event::TraceEventHandle
AddTraceEventWithThreadIdAndTimestamp(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    int thread_id,
    const base::TimeTicks& timestamp,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    const ARG1_TYPE& arg1_val) {
  const int num_args = 1;
  unsigned char arg_types[1];
  unsigned long long arg_values[1];
  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
  return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
      phase, category_group_enabled, name, scope, id, bind_id, thread_id,
      timestamp, num_args, &arg1_name, arg_types, arg_values, NULL, flags);
}

template<class ARG1_TYPE>
static inline base::trace_event::TraceEventHandle AddTraceEvent(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    const ARG1_TYPE& arg1_val) {
  int thread_id = static_cast<int>(base::PlatformThread::CurrentId());
  base::TimeTicks now = base::TimeTicks::Now();
  return AddTraceEventWithThreadIdAndTimestamp(
      phase, category_group_enabled, name, scope, id, thread_id, now, flags,
      bind_id, arg1_name, arg1_val);
}

template <class ARG1_CONVERTABLE_TYPE>
static inline base::trace_event::TraceEventHandle AddTraceEvent(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    std::unique_ptr<ARG1_CONVERTABLE_TYPE> arg1_val) {
  int thread_id = static_cast<int>(base::PlatformThread::CurrentId());
  base::TimeTicks now = base::TimeTicks::Now();
  return AddTraceEventWithThreadIdAndTimestamp(
      phase, category_group_enabled, name, scope, id, thread_id, now, flags,
      bind_id, arg1_name, std::move(arg1_val));
}

template<class ARG1_TYPE, class ARG2_TYPE>
static inline base::trace_event::TraceEventHandle
AddTraceEventWithThreadIdAndTimestamp(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    int thread_id,
    const base::TimeTicks& timestamp,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    const ARG1_TYPE& arg1_val,
    const char* arg2_name,
    const ARG2_TYPE& arg2_val) {
  const int num_args = 2;
  const char* arg_names[2] = { arg1_name, arg2_name };
  unsigned char arg_types[2];
  unsigned long long arg_values[2];
  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
  SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
  return TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
      phase, category_group_enabled, name, scope, id, bind_id, thread_id,
      timestamp, num_args, arg_names, arg_types, arg_values, NULL, flags);
}

template <class ARG1_CONVERTABLE_TYPE, class ARG2_TYPE>
static inline base::trace_event::TraceEventHandle AddTraceEvent(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    std::unique_ptr<ARG1_CONVERTABLE_TYPE> arg1_val,
    const char* arg2_name,
    const ARG2_TYPE& arg2_val) {
  int thread_id = static_cast<int>(base::PlatformThread::CurrentId());
  base::TimeTicks now = base::TimeTicks::Now();
  return AddTraceEventWithThreadIdAndTimestamp(
      phase, category_group_enabled, name, scope, id, thread_id, now, flags,
      bind_id, arg1_name, std::move(arg1_val), arg2_name, arg2_val);
}

template <class ARG1_TYPE, class ARG2_CONVERTABLE_TYPE>
static inline base::trace_event::TraceEventHandle AddTraceEvent(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    const ARG1_TYPE& arg1_val,
    const char* arg2_name,
    std::unique_ptr<ARG2_CONVERTABLE_TYPE> arg2_val) {
  int thread_id = static_cast<int>(base::PlatformThread::CurrentId());
  base::TimeTicks now = base::TimeTicks::Now();
  return AddTraceEventWithThreadIdAndTimestamp(
      phase, category_group_enabled, name, scope, id, thread_id, now, flags,
      bind_id, arg1_name, arg1_val, arg2_name, std::move(arg2_val));
}

template <class ARG1_CONVERTABLE_TYPE, class ARG2_CONVERTABLE_TYPE>
static inline base::trace_event::TraceEventHandle AddTraceEvent(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    std::unique_ptr<ARG1_CONVERTABLE_TYPE> arg1_val,
    const char* arg2_name,
    std::unique_ptr<ARG2_CONVERTABLE_TYPE> arg2_val) {
  int thread_id = static_cast<int>(base::PlatformThread::CurrentId());
  base::TimeTicks now = base::TimeTicks::Now();
  return AddTraceEventWithThreadIdAndTimestamp(
      phase, category_group_enabled, name, scope, id, thread_id, now, flags,
      bind_id, arg1_name, std::move(arg1_val), arg2_name, std::move(arg2_val));
}

template<class ARG1_TYPE, class ARG2_TYPE>
static inline base::trace_event::TraceEventHandle AddTraceEvent(
    char phase,
    const unsigned char* category_group_enabled,
    const char* name,
    const char* scope,
    unsigned long long id,
    unsigned int flags,
    unsigned long long bind_id,
    const char* arg1_name,
    const ARG1_TYPE& arg1_val,
    const char* arg2_name,
    const ARG2_TYPE& arg2_val) {
  int thread_id = static_cast<int>(base::PlatformThread::CurrentId());
  base::TimeTicks now = base::TimeTicks::Now();
  return AddTraceEventWithThreadIdAndTimestamp(
      phase, category_group_enabled, name, scope, id, thread_id, now, flags,
      bind_id, arg1_name, arg1_val, arg2_name, arg2_val);
}

template <class ARG1_CONVERTABLE_TYPE>
static inline void AddMetadataEvent(
    const unsigned char* category_group_enabled,
    const char* event_name,
    const char* arg_name,
    std::unique_ptr<ARG1_CONVERTABLE_TYPE> arg_value) {
  const char* arg_names[1] = {arg_name};
  unsigned char arg_types[1] = {TRACE_VALUE_TYPE_CONVERTABLE};
  std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
      convertable_values[1] = {std::move(arg_value)};
  base::trace_event::TraceLog::GetInstance()->AddMetadataEvent(
      category_group_enabled, event_name,
      1,  // num_args
      arg_names, arg_types,
      nullptr,  // arg_values
      convertable_values, TRACE_EVENT_FLAG_NONE);
}

template <class ARG1_TYPE>
static void AddMetadataEvent(const unsigned char* category_group_enabled,
                             const char* event_name,
                             const char* arg_name,
                             const ARG1_TYPE& arg_val) {
  const int num_args = 1;
  const char* arg_names[1] = {arg_name};
  unsigned char arg_types[1];
  unsigned long long arg_values[1];
  SetTraceValue(arg_val, &arg_types[0], &arg_values[0]);

  base::trace_event::TraceLog::GetInstance()->AddMetadataEvent(
      category_group_enabled, event_name, num_args, arg_names, arg_types,
      arg_values, nullptr, TRACE_EVENT_FLAG_NONE);
}

// Used by TRACE_EVENTx macros. Do not use directly.
class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
 public:
  // Note: members of data_ intentionally left uninitialized. See Initialize.
  ScopedTracer() : p_data_(NULL) {}

  ~ScopedTracer() {
    if (p_data_ && *data_.category_group_enabled)
      TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
          data_.category_group_enabled, data_.name, data_.event_handle);
  }

  void Initialize(const unsigned char* category_group_enabled,
                  const char* name,
                  base::trace_event::TraceEventHandle event_handle) {
    data_.category_group_enabled = category_group_enabled;
    data_.name = name;
    data_.event_handle = event_handle;
    p_data_ = &data_;
  }

 private:
  // This Data struct workaround is to avoid initializing all the members
  // in Data during construction of this object, since this object is always
  // constructed, even when tracing is disabled. If the members of Data were
  // members of this class instead, compiler warnings occur about potential
  // uninitialized accesses.
  struct Data {
    const unsigned char* category_group_enabled;
    const char* name;
    base::trace_event::TraceEventHandle event_handle;
  };
  Data* p_data_;
  Data data_;
};

// Used by TRACE_EVENT_BINARY_EFFICIENTx macro. Do not use directly.
class TRACE_EVENT_API_CLASS_EXPORT ScopedTraceBinaryEfficient {
 public:
  ScopedTraceBinaryEfficient(const char* category_group, const char* name);
  ~ScopedTraceBinaryEfficient();

 private:
  const unsigned char* category_group_enabled_;
  const char* name_;
  base::trace_event::TraceEventHandle event_handle_;
};

// This macro generates less code then TRACE_EVENT0 but is also
// slower to execute when tracing is off. It should generally only be
// used with code that is seldom executed or conditionally executed
// when debugging.
// For now the category_group must be "gpu".
#define TRACE_EVENT_BINARY_EFFICIENT0(category_group, name) \
    trace_event_internal::ScopedTraceBinaryEfficient \
        INTERNAL_TRACE_EVENT_UID(scoped_trace)(category_group, name);

// TraceEventSamplingStateScope records the current sampling state
// and sets a new sampling state. When the scope exists, it restores
// the sampling state having recorded.
template<size_t BucketNumber>
class TraceEventSamplingStateScope {
 public:
  TraceEventSamplingStateScope(const char* category_and_name) {
    previous_state_ = TraceEventSamplingStateScope<BucketNumber>::Current();
    TraceEventSamplingStateScope<BucketNumber>::Set(category_and_name);
  }

  ~TraceEventSamplingStateScope() {
    TraceEventSamplingStateScope<BucketNumber>::Set(previous_state_);
  }

  static inline const char* Current() {
    return reinterpret_cast<const char*>(TRACE_EVENT_API_ATOMIC_LOAD(
      g_trace_state[BucketNumber]));
  }

  static inline void Set(const char* category_and_name) {
    TRACE_EVENT_API_ATOMIC_STORE(
      g_trace_state[BucketNumber],
      reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>(
        const_cast<char*>(category_and_name)));
  }

 private:
  const char* previous_state_;
};

}  // namespace trace_event_internal

namespace base {
namespace trace_event {

template<typename IDType> class TraceScopedTrackableObject {
 public:
  TraceScopedTrackableObject(const char* category_group, const char* name,
      IDType id)
    : category_group_(category_group),
      name_(name),
      id_(id) {
    TRACE_EVENT_OBJECT_CREATED_WITH_ID(category_group_, name_, id_);
  }

  template <typename ArgType> void snapshot(ArgType snapshot) {
    TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(category_group_, name_, id_, snapshot);
  }

  ~TraceScopedTrackableObject() {
    TRACE_EVENT_OBJECT_DELETED_WITH_ID(category_group_, name_, id_);
  }

 private:
  const char* category_group_;
  const char* name_;
  IDType id_;

  DISALLOW_COPY_AND_ASSIGN(TraceScopedTrackableObject);
};

}  // namespace trace_event
}  // namespace base

#endif  // BASE_TRACE_EVENT_TRACE_EVENT_H_