[Android] Short-circuit touch forwarding when no touch handlers exist

content/browser/renderer_host/input/input_router_impl.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/input_router_impl.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 293 matching lines @@
   FilterAndSendWebInputEvent(gesture_event.event, gesture_event.latency, false);
 }
 
 const NativeWebKeyboardEvent* InputRouterImpl::GetLastKeyboardEvent() const {
   if (key_queue_.empty())
     return NULL;
   return &key_queue_.front();
 }
 
 bool InputRouterImpl::ShouldForwardTouchEvent() const {
-  // Always send a touch event if the renderer has a touch-event handler.
-  return touch_event_queue_->has_handlers();
+  // Always send a touch event if the renderer has a touch-event handler or
+  // there are pending touch events.
+  return touch_event_queue_->has_handlers() || !touch_event_queue_->empty();
 }
 
 void InputRouterImpl::OnViewUpdated(int view_flags) {
   current_view_flags_ = view_flags;
 
   // A fixed page scale or mobile viewport should disable the touch ack timeout.
   UpdateTouchAckTimeoutEnabled();
 }
 
 bool InputRouterImpl::OnMessageReceived(const IPC::Message& message) {
@@ skipping 481 matching lines @@
   touch_event_queue_->SetAckTimeoutEnabled(touch_ack_timeout_enabled,
                                            touch_ack_timeout_delay_);
 }
 
 bool InputRouterImpl::IsInOverscrollGesture() const {
   OverscrollController* controller = client_->GetOverscrollController();
   return controller && controller->overscroll_mode() != OVERSCROLL_NONE;
 }
 
 }  // namespace content