Add latency measurement system

cc/output_surface.h

Index: cc/output_surface.h
diff --git a/cc/output_surface.h b/cc/output_surface.h
index 3d62f184fbc8b30ac6aa0a948a7c7d81799a0df0..239b3974059ffe1a0e410114d07d4ff2389a0bba 100644
--- a/cc/output_surface.h
+++ b/cc/output_surface.h
@@ -19,6 +19,7 @@ namespace cc {
 class CompositorFrame;
 class OutputSurfaceClient;
 class SoftwareOutputDevice;
+struct LatencyInfo;
 
 // Represents the output surface for a compositor. The compositor owns
 // and manages its destruction. Its lifetime is:
@@ -56,6 +57,8 @@ class CC_EXPORT OutputSurface : public WebKit::WebCompositorOutputSurface {
   // Sends frame data to the parent compositor. This should only be called when
   // capabilities().has_parent_compositor.
   virtual void SendFrameToParentCompositor(const CompositorFrame&) {}
+
+  virtual void SetLatencyInfo(const LatencyInfo&) {}
 };
 
 }  // namespace cc