cc:: Add LatencyQuery logic back into OutputSurface.

cc/output/output_surface.h

Index: cc/output/output_surface.h
diff --git a/cc/output/output_surface.h b/cc/output/output_surface.h
index 42498c8451e12594d0d8e377cacfefd9456b9b06..d3eca54fa83d98023e0c71e623785a5fd8422d8c 100644
--- a/cc/output/output_surface.h
+++ b/cc/output/output_surface.h
@@ -12,6 +12,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "cc/base/cc_export.h"
+#include "cc/base/rolling_time_delta_history.h"
 #include "cc/output/context_provider.h"
 #include "cc/output/overlay_candidate_validator.h"
 #include "cc/output/software_output_device.h"
@@ -127,6 +128,10 @@ class CC_EXPORT OutputSurface {
 
   bool HasClient() { return !!client_; }
 
+  // Returns an estimate of the current GPU latency. When only a software
+  // device is present, returns 0.
+  base::TimeDelta GpuLatencyEstimate();
+
   // Get the class capable of informing cc of hardware overlay capability.
   OverlayCandidateValidator* overlay_candidate_validator() const {
     return overlay_candidate_validator_.get();
@@ -169,11 +174,16 @@ class CC_EXPORT OutputSurface {
   void SetUpContext3d();
   void ResetContext3d();
   void SetMemoryPolicy(const ManagedMemoryPolicy& policy);
+  void UpdateAndMeasureGpuLatency();
 
   bool external_stencil_test_enabled_;
 
   base::WeakPtrFactory<OutputSurface> weak_ptr_factory_;
 
+  std::deque<unsigned> available_gpu_latency_query_ids_;
+  std::deque<unsigned> pending_gpu_latency_query_ids_;
+  RollingTimeDeltaHistory gpu_latency_history_;
+
   DISALLOW_COPY_AND_ASSIGN(OutputSurface);
 };