Make tapDown async.

content/browser/renderer_host/input/gesture_event_filter.h

Index: content/browser/renderer_host/input/gesture_event_filter.h
diff --git a/content/browser/renderer_host/input/gesture_event_filter.h b/content/browser/renderer_host/input/gesture_event_filter.h
index b0c378222eaa1d19ab320500a7c9f62231cd4323..121c54ed26292fab950f5503da77edcf6668ee13 100644
--- a/content/browser/renderer_host/input/gesture_event_filter.h
+++ b/content/browser/renderer_host/input/gesture_event_filter.h
@@ -77,6 +77,8 @@ class GestureEventFilter {
   void ForwardGestureEventSkipDeferral(
       const GestureEventWithLatencyInfo& gesture_event);
 
+  static bool IsGestureEventTypeAsync(int type);

[jdduke (slow), 2013/09/30 15:42:56]

Please use the enum type directly, WebInputEvent::Type.

[tdresser, 2013/09/30 18:05:03]

Done.

+
  private:
   friend class MockRenderWidgetHost;
   friend class ImmediateInputRouterTest;
@@ -146,6 +148,8 @@ class GestureEventFilter {
   gfx::Transform GetTransformForEvent(
       const GestureEventWithLatencyInfo& gesture_event) const;
 
+  void SendAsynchEvents();

[jdduke (slow), 2013/09/30 15:42:56]

nit: SendAsyncEvents();

Hmm, actually, there are a few "asynch" additions in the patch, could you change
to "async"?

[tdresser, 2013/09/30 18:05:03]

Done.

+
   // The receiver of all forwarded gesture events.
   InputRouter* input_router_;
 
@@ -183,7 +187,9 @@ class GestureEventFilter {
 
   typedef std::deque<GestureEventWithLatencyInfo> GestureEventQueue;
 
-  // Queue of coalesced gesture events not yet sent to the renderer.
+  // Queue of coalesced gesture events not yet sent to the
+  // renderer. The event at the front of the queue has been sent and
+  // is awaiting an ACK. All other events have yet to be sent.

[jdduke (slow), 2013/09/30 15:42:56]

I don't know that this is always true, e.g., we sometimes send a
ScrollBy/PinchBy gesture pair, ignoring one of the returned acks.  Might be
worth a mention (something about |ignore_next_ack_|)?

[tdresser, 2013/09/30 18:05:03]

Done. Can you double check that the new comment is correct?

   GestureEventQueue coalesced_gesture_events_;
 
   // Tap gesture event currently subject to deferral.