Add latency measurement system

content/renderer/gpu/input_event_filter.h

Index: content/renderer/gpu/input_event_filter.h
diff --git a/content/renderer/gpu/input_event_filter.h b/content/renderer/gpu/input_event_filter.h
index 690e9bdf0c42a5075db26e11de1fc22238b19def..bf178460ca5723f75f5c909afbd7feb0343f8bef 100644
--- a/content/renderer/gpu/input_event_filter.h
+++ b/content/renderer/gpu/input_event_filter.h
@@ -29,6 +29,7 @@ class CONTENT_EXPORT InputEventFilter
     : public IPC::ChannelProxy::MessageFilter {
  public:
   typedef base::Callback<void(int /*routing_id*/,
+                              int64 /*input_number*/,
                               const WebKit::WebInputEvent*)> Handler;
 
   // The |handler| is invoked on the thread associated with |target_loop| to
@@ -63,7 +64,8 @@ class CONTENT_EXPORT InputEventFilter
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
   // Expects a ViewMsg_HandleInputEvent message.
-  static const WebKit::WebInputEvent* CrackMessage(const IPC::Message& message);
+  static const WebKit::WebInputEvent* CrackMessage(const IPC::Message& message,
+      int64* frame_number);
 
  private:
   friend class IPC::ChannelProxy::MessageFilter;