Added support for GPU Tracing on mobile devices which support it.

gpu/command_buffer/service/gpu_tracer.h

Index: gpu/command_buffer/service/gpu_tracer.h
diff --git a/gpu/command_buffer/service/gpu_tracer.h b/gpu/command_buffer/service/gpu_tracer.h
index 5aa2cd8a4e07e49ab5379a8fa344c9891ed0a498..1d04777dfad391c8a7cddbc602aa6b72be854c64 100644
--- a/gpu/command_buffer/service/gpu_tracer.h
+++ b/gpu/command_buffer/service/gpu_tracer.h
@@ -33,6 +33,13 @@ enum GpuTracerSource {
   NUM_TRACER_SOURCES
 };
 
+enum GpuTracerType {
+  kTracerTypeInvalid = -1,
+
+  kTracerTypeARBTimer,
+  kTracerTypeDisjointTimer
+};
+
 // Marker structure for a Trace.
 struct TraceMarker {
   TraceMarker(const std::string& name);
@@ -60,6 +67,9 @@ class GPUTracer : public base::SupportsWeakPtr<GPUTracer> {
   // End the last started trace marker.
   bool End(GpuTracerSource source);
 
+  // Discard data obtained from current trace.
+  void DiscardTrace();
+
   bool IsTracing();
 
   // Retrieve the name of the current open trace.
@@ -86,7 +96,7 @@ class GPUTracer : public base::SupportsWeakPtr<GPUTracer> {
   int64 timer_offset_;
   GpuTracerSource last_tracer_source_;
 
-  bool enabled_;
+  GpuTracerType tracer_type_;
   bool gpu_timing_synced_;
   bool gpu_executing_;
   bool process_posted_;
@@ -126,18 +136,19 @@ class TraceOutputter : public Outputter {
 class GPU_EXPORT GPUTrace
     : public base::RefCounted<GPUTrace> {
  public:
-  explicit GPUTrace(const std::string& name);
   GPUTrace(scoped_refptr<Outputter> outputter,
            const std::string& name,
-           int64 offset);
+           int64 offset,
+           GpuTracerType tracer_type);
 
-  bool IsEnabled() { return enabled_; }
+  bool IsEnabled() { return tracer_type_ != kTracerTypeInvalid; }
   const std::string& name() { return name_; }
 
   void Start();
   void End();
   bool IsAvailable();
   void Process();
+  void DiscardTrace();
 
  private:
   ~GPUTrace();
@@ -152,8 +163,9 @@ class GPU_EXPORT GPUTrace
   int64 offset_;
   int64 start_time_;
   int64 end_time_;
+  GpuTracerType tracer_type_;
   bool end_requested_;
-  bool enabled_;
+  bool discard_trace_;
 
   GLuint queries_[2];