Defer flushing the touch queue when all touch handlers removed

content/browser/renderer_host/input/touch_event_queue.cc

 // 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.
 
 #include "content/browser/renderer_host/input/touch_event_queue.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/stl_util.h"
 #include "content/browser/renderer_host/input/timeout_monitor.h"
@@ skipping 619 matching lines @@
       touch_filtering_state_ = DROP_TOUCHES_IN_SEQUENCE;
     }
   } else {
     // TODO(jdduke): Synthesize a TouchCancel if necessary to update Blink touch
     // state tracking and/or touch-action filtering (e.g., if the touch handler
     // was removed mid-sequence), crbug.com/375940.
     touch_filtering_state_ = DROP_ALL_TOUCHES;
     pending_async_touchmove_.reset();
     if (timeout_handler_)
       timeout_handler_->Reset();
-    if (!touch_queue_.empty())
-      ProcessTouchAck(INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS, LatencyInfo());
-    // As there is no touch handler, ack'ing the event should flush the queue.
-    DCHECK(touch_queue_.empty());
   }
 }
 
 bool TouchEventQueue::IsPendingAckTouchStart() const {
   DCHECK(!dispatching_touch_ack_);
   if (touch_queue_.empty())
     return false;
 
   const blink::WebTouchEvent& event =
       touch_queue_.front()->coalesced_event().event;
@@ skipping 166 matching lines @@
        iter != end;
        ++iter) {
     if (iter->second != ack_state)
       return false;
   }
 
   return true;
 }
 
 }  // namespace content