Coalesce async touch move events until the ack back from render

content/browser/renderer_host/input/input_router_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_INPUT_INPUT_ROUTER_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_INPUT_ROUTER_IMPL_H_
 
 #include <queue>
 
 #include "base/basictypes.h"
@@ skipping 124 matching lines @@
   // Indicates the source of an ack provided to |ProcessInputEventAck()|.
   // The source is tracked by |current_ack_source_|, which aids in ack routing.
   enum AckSource {
     RENDERER,
     CLIENT,
     IGNORING_DISPOSITION,
     ACK_SOURCE_NONE
   };
   // Note: This function may result in |this| being deleted, and as such
   // should be the last method called in any internal chain of event handling.
   void ProcessInputEventAck(blink::WebInputEvent::Type event_type,

[jdduke (slow), 2015/05/01 19:11:09]

What if we add a

struct InputEventAck {
  type, state, latency, overscroll, unique_touch;
};

with a few helper constructors? We could put that in content/common/input.
Thoughts? That would simplify a number of these functions, and eventually will
let us generalize the ack quite simply.

                             InputEventAckState ack_result,
                             const ui::LatencyInfo& latency_info,
+                            const uint32 unique_touch_event_id,
                             AckSource ack_source);
 
   // Dispatches the ack'ed event to |ack_handler_|.
   void ProcessKeyboardAck(blink::WebInputEvent::Type type,
                           InputEventAckState ack_result);
 
   // Forwards a valid |next_mouse_move_| if |type| is MouseMove.
   void ProcessMouseAck(blink::WebInputEvent::Type type,
                        InputEventAckState ack_result);
 
   // Dispatches the ack'ed event to |ack_handler_|, forwarding queued events
   // from |coalesced_mouse_wheel_events_|.
   void ProcessWheelAck(InputEventAckState ack_result,
                        const ui::LatencyInfo& latency);
 
   // Forwards the event ack to |gesture_event_queue|, potentially triggering
   // dispatch of queued gesture events.
   void ProcessGestureAck(blink::WebInputEvent::Type type,
                          InputEventAckState ack_result,
                          const ui::LatencyInfo& latency);
 
   // Forwards the event ack to |touch_event_queue_|, potentially triggering
   // dispatch of queued touch events, or the creation of gesture events.
   void ProcessTouchAck(InputEventAckState ack_result,
-                       const ui::LatencyInfo& latency);
+                       const ui::LatencyInfo& latency,
+                       const uint32 unique_touch_event_id);
 
   // Called when a touch timeout-affecting bit has changed, in turn toggling the
   // touch ack timeout feature of the |touch_event_queue_| as appropriate. Input
   // to that determination includes current view properties and the allowed
   // touch action. Note that this will only affect platforms that have a
   // non-zero touch timeout configuration.
   void UpdateTouchAckTimeoutEnabled();
 
   // If a flush has been requested, signals a completed flush to the client if
   // all events have been dispatched (i.e., |HasPendingEvents()| is false).
@@ skipping 69 matching lines @@
   TouchActionFilter touch_action_filter_;
   InputEventStreamValidator input_stream_validator_;
   InputEventStreamValidator output_stream_validator_;
 
   DISALLOW_COPY_AND_ASSIGN(InputRouterImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_INPUT_ROUTER_IMPL_H_