Coalesce async touch move events until the ack back from render

content/common/input_messages.h

 // Copyright (c) 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.
 
 // IPC messages for input events and other messages that require processing in
 // order relative to input events.
 // Multiply-included message file, hence no include guard.
 
 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
@@ skipping 96 matching lines @@
 IPC_STRUCT_TRAITS_END()
 
 IPC_STRUCT_BEGIN(InputHostMsg_HandleInputEvent_ACK_Params)
   IPC_STRUCT_MEMBER(blink::WebInputEvent::Type, type)
   IPC_STRUCT_MEMBER(content::InputEventAckState, state)
   IPC_STRUCT_MEMBER(ui::LatencyInfo, latency)
   // TODO(jdduke): Use Optional<T> type to avoid heap alloc, crbug.com/375002.
   IPC_STRUCT_MEMBER(scoped_ptr<content::DidOverscrollParams>, overscroll)
 IPC_STRUCT_END()
 
+IPC_STRUCT_BEGIN(InputHostMsg_HandleUncancelableTouchMoveEvent_ACK_Params)
+IPC_STRUCT_END()
+
 // Sends an input event to the render widget.
 IPC_MESSAGE_ROUTED3(InputMsg_HandleInputEvent,
                     IPC::WebInputEventPointer /* event */,
                     ui::LatencyInfo /* latency_info */,
                     bool /* is_keyboard_shortcut */)
 
 // Sends the cursor visibility state to the render widget.
 IPC_MESSAGE_ROUTED1(InputMsg_CursorVisibilityChange,
                     bool /* is_visible */)
 
@@ skipping 107 matching lines @@
 
 IPC_MESSAGE_ROUTED0(InputMsg_SyntheticGestureCompleted)
 
 // -----------------------------------------------------------------------------
 // Messages sent from the renderer to the browser.
 
 // Acknowledges receipt of a InputMsg_HandleInputEvent message.
 IPC_MESSAGE_ROUTED1(InputHostMsg_HandleInputEvent_ACK,
                     InputHostMsg_HandleInputEvent_ACK_Params)
 
+IPC_MESSAGE_ROUTED1(InputHostMsg_HandleUncancelableTouchMoveEvent_ACK,

[jdduke (slow), 2015/03/30 18:04:15]

Can we just make this 

IPC_MESSAGE_ROUTED0(InputHostMsg_HandleUncancelableTouchMoveEvent_ACK);

[lanwei, 2015/03/31 13:07:49]

Done.

+                    InputHostMsg_HandleUncancelableTouchMoveEvent_ACK_Params)
+
 IPC_MESSAGE_ROUTED1(InputHostMsg_QueueSyntheticGesture,
                     content::SyntheticGesturePacket)
 
 // Notifies the allowed touch actions for a new touch point.
 IPC_MESSAGE_ROUTED1(InputHostMsg_SetTouchAction,
                     content::TouchAction /* touch_action */)
 
 // Sent by the compositor when input scroll events are dropped due to bounds
 // restrictions on the root scroll offset.
 IPC_MESSAGE_ROUTED1(InputHostMsg_DidOverscroll,
@@ skipping 14 matching lines @@
 // This IPC message sends the character bounds after every composition change
 // to always have correct bound info.
 IPC_MESSAGE_ROUTED2(InputHostMsg_ImeCompositionRangeChanged,
                     gfx::Range /* composition range */,
                     std::vector<gfx::Rect> /* character bounds */)
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent InputMsg, then ifdefs for platform specific InputMsg, then
 // platform independent InputHostMsg, then ifdefs for platform specific
 // InputHostMsg.