Add telemetry to track the time an event spent waiting for the main thread.

content/browser/renderer_host/input/immediate_input_router.h

Index: content/browser/renderer_host/input/immediate_input_router.h
diff --git a/content/browser/renderer_host/input/immediate_input_router.h b/content/browser/renderer_host/input/immediate_input_router.h
index 270ca3dc67e086230811e7079e299236e13b1225..18030cdb33b4ad542cd2b8cb1f1a4fc9cbba7c79 100644
--- a/content/browser/renderer_host/input/immediate_input_router.h
+++ b/content/browser/renderer_host/input/immediate_input_router.h
@@ -119,7 +119,9 @@ private:
   // Called by ProcessInputEventAck() to process a gesture event ack message.
   // This validates the gesture for suppression of touchpad taps and sends one
   // previously queued coalesced gesture if it exists.
-  void ProcessGestureAck(int type, InputEventAckState ack_result);
+  void ProcessGestureAck(int type,
+                         InputEventAckState ack_result,

[nduca, 2013/08/15 01:41:04]

here you're changing just the gesture ack but not the others. This is a sign to
me of something not fully thought out... why gesture but not anything else?

+                         const ui::LatencyInfo& latency_info);
 
   // Called on ProcessInputEventAck() to process a touch event ack message.
   // This can result in a gesture event being generated and sent back to the