Extend the hang monitor timeout when an event ack is received.

content/browser/renderer_host/render_widget_host_impl.cc

 // Copyright (c) 2012 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/render_widget_host_impl.h"
 
 #include <math.h>
 #include <set>
 #include <utility>
 
@@ skipping 1761 matching lines @@
 }
 
 void RenderWidgetHostImpl::IncrementInFlightEventCount() {
   StartHangMonitorTimeout(
       TimeDelta::FromMilliseconds(hung_renderer_delay_ms_));
   increment_in_flight_event_count();
 }
 
 void RenderWidgetHostImpl::DecrementInFlightEventCount() {
   DCHECK_GE(in_flight_event_count_, 0);
-  // Cancel pending hung renderer checks since the renderer is responsive.
-  if (decrement_in_flight_event_count() <= 0)
+  if (decrement_in_flight_event_count() <= 0) {
+    // Cancel pending hung renderer checks since the renderer is responsive.
     StopHangMonitorTimeout();
+  } else {
+    // The renderer is responsive, but there are in-flight events to wait for.
+    RestartHangMonitorTimeout();
+  }
 }
 
 void RenderWidgetHostImpl::OnHasTouchEventHandlers(bool has_handlers) {
   has_touch_handler_ = has_handlers;
 }
 
 void RenderWidgetHostImpl::DidFlush() {
   if (synthetic_gesture_controller_)
     synthetic_gesture_controller_->OnDidFlushInput();
   if (view_)
@@ skipping 516 matching lines @@
 }
 #endif
 
 SkColorType RenderWidgetHostImpl::PreferredReadbackFormat() {
   if (view_)
     return view_->PreferredReadbackFormat();
   return kN32_SkColorType;
 }
 
 }  // namespace content