Coalesce async touch move events until the ack back from render

content/browser/renderer_host/input/touch_event_queue.h

Index: content/browser/renderer_host/input/touch_event_queue.h
diff --git a/content/browser/renderer_host/input/touch_event_queue.h b/content/browser/renderer_host/input/touch_event_queue.h
index a61b90d8eca8c1707d31b3e9bfbadabb175047a0..6c4aed95195e72260b470fe791149a7ddf3010a7 100644
--- a/content/browser/renderer_host/input/touch_event_queue.h
+++ b/content/browser/renderer_host/input/touch_event_queue.h
@@ -66,6 +66,8 @@ class CONTENT_EXPORT TouchEventQueue {
   void ProcessTouchAck(InputEventAckState ack_result,
                        const ui::LatencyInfo& latency_info);
 
+  void ProcessAsyncTouchAck();

[tdresser, 2015/03/23 19:21:44]

This should probably be ProcessUncancelableTouchAck.

[lanwei, 2015/03/24 18:46:38]

Done.

+
   // When GestureScrollBegin is received, we send a touch cancel to renderer,
   // route all the following touch events directly to client, and ignore the
   // ack for the touch cancel. When Gesture{ScrollEnd,FlingStart} is received,
@@ -201,7 +203,18 @@ class CONTENT_EXPORT TouchEventQueue {
   // until a sufficient time period has elapsed since the last sent touch event.
   // For details see the design doc at http://goo.gl/lVyJAa.
   bool send_touch_events_async_;
+
+  // Whether we receive an ack from render for async touch move event.
+  bool receive_async_touch_move_ack_;

[tdresser, 2015/03/23 19:21:44]

Can you clarify this comment? When wouldn't we receive an ack for an async touch
move event? Also, do you mean async, or uncancelable?

[lanwei, 2015/03/24 18:46:38]

Done.

   scoped_ptr<TouchEventWithLatencyInfo> pending_async_touchmove_;
+
+  // Once this value is greater than 0, which means we should ignore the
+  // following ignore_ack_ numbers of acks from render for async touch moves.
+  int ignore_ack_;

[tdresser, 2015/03/23 19:21:44]

The variable name here should indicate that this is a number.

Perhaps: pending_uncancelable_event_ack_count_, or something along those lines.

I'm not clear on the difference between this and |sent_async_touch_move_count_|.

[lanwei, 2015/03/24 18:46:38]

Done.

+
+  // Count the number of aysnc touch moves sent out are waiting for their ack

[tdresser, 2015/03/23 19:21:44]

Fix spelling "aysnc"

[lanwei, 2015/03/24 18:46:38]

Done.

+  // back from render.
+  int sent_async_touch_move_count_;
   double last_sent_touch_timestamp_sec_;
 
   // Event is saved to compare pointer positions for new touchmove events.