78   Queue() : head_(NULL), last_(NULL), size_(0) {}  in Queue()
85     if (size_ > 0) {  in Clear()
98       size_ = 0;  in Clear()
103   size_t Size() const { return size_; }  in Size()
120     if (size_ == 0) {  in Enqueue()
122       size_ = 1;  in Enqueue()
126       size_++;  in Enqueue()
133     if (size_ == 0) {  in Dequeue()
139     size_--;  in Dequeue()
140     if (size_ == 0) {  in Dequeue()
166   size_t size_;  // The number of elements in the queue.  variable