Add latency measurement system

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index 631455f45d10566602bcae04ec36303b14265bcb..ca0648ba9a6b7f04936158d7f2c131c82f9c6971 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -32,6 +32,7 @@
 #include "ui/gfx/rect.h"
 #include "ui/gfx/vector2d.h"
 #include "ui/surface/transport_dib.h"
+#include "webkit/compositor_bindings/web_latency_info_impl.h"
 #include "webkit/glue/webcursor.h"
 
 struct ViewHostMsg_UpdateRect_Params;
@@ -115,6 +116,7 @@ class CONTENT_EXPORT RenderWidget
 
   // WebKit::WebWidgetClient
   virtual void willBeginCompositorFrame();
+  virtual void didBeginCompositorFrame();
   virtual void didInvalidateRect(const WebKit::WebRect&);
   virtual void didScrollRect(int dx, int dy,
                              const WebKit::WebRect& clipRect);
@@ -265,8 +267,10 @@ class CONTENT_EXPORT RenderWidget
   void OnCreateVideoAck(int32 video_id);
   void OnUpdateVideoAck(int32 video_id);
   void OnRequestMoveAck();
-  void OnHandleInputEvent(const WebKit::WebInputEvent* event,
+  void OnHandleInputEvent(int64 input_number,
+                          const WebKit::WebInputEvent* event,
                           bool keyboard_shortcut);
+  void OnStartFrame(int64 input_number);
   void OnMouseCaptureLost();
   virtual void OnSetFocus(bool enable);
   void OnSetInputMethodActive(bool is_active);
@@ -441,6 +445,10 @@ class CONTENT_EXPORT RenderWidget
   // the scheduling of compositing requests.
   virtual bool WebWidgetHandlesCompositorScheduling() const;
 
+  // Signal that a new frame is starting, for the purposes of keeping track of
+  // frame latency.
+  void StartingFrame();
+
   // Routing ID that allows us to communicate to the parent browser process
   // RenderWidgetHost. When MSG_ROUTING_NONE, no messages may be sent.
   int32 routing_id_;
@@ -629,6 +637,13 @@ class CONTENT_EXPORT RenderWidget
   // Specified whether the compositor will run in its own thread.
   bool is_threaded_compositing_enabled_;
 
+  // Captures information about what input events and frames are currently
+  // being processed.
+  bool started_frame_;
+  bool got_input_;
+
+  WebKit::WebLatencyInfoImpl latency_info_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };