Fixing a problem, where a hung renderer process is not killed when navigating away

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 7476989ec27f02a40b198ad4f5fde1eaa86d9125..992c4f5a1b4c699bb7ad977e552b30ae779cecf2 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -628,9 +628,12 @@ void RenderWidgetHostImpl::StartHangMonitorTimeout(TimeDelta delay) {
     return;
   }
 
-  // Set time_when_considered_hung_ if it's null.
+  // Set time_when_considered_hung_ if it's null, or if it is further in the

[Charlie Reis, 2012/04/06 22:34:14]

nit: Split this into a separate sentence to make it easier to read.  Something
like "Otherwise, update time_when_considered_hung_ if the requested end time is
now sooner than before."

I don't suppose we have any unit tests for this logic, do we?  If we do, it
would be nice to add one for this case.

[nasko, 2012/04/10 00:16:37]

No, there is no unit test for this particular case. I will add one, as there is
an existing unit test for that timer.

+  // future than the current request, update it to the shorter duration. This
+  // will have the side effect that the existing timeout will be forgotten.
   Time requested_end_time = Time::Now() + delay;
-  if (time_when_considered_hung_.is_null())
+  if (time_when_considered_hung_.is_null() ||
+      time_when_considered_hung_ > requested_end_time)
     time_when_considered_hung_ = requested_end_time;
 
   // If we already have a timer with the same or shorter duration, then we can
@@ -845,7 +848,7 @@ void RenderWidgetHostImpl::ForwardInputEvent(const WebInputEvent& input_event,
   // after this line.
   next_mouse_move_.reset();
 
-  in_flight_event_count_++;
+  IncrementInFlightEventCount();
   StartHangMonitorTimeout(
       TimeDelta::FromMilliseconds(hung_renderer_delay_ms_));
 }
@@ -1287,7 +1290,7 @@ void RenderWidgetHostImpl::OnMsgInputEventAck(WebInputEvent::Type event_type,
   UMA_HISTOGRAM_TIMES("MPArch.RWH_InputEventDelta", delta);
 
   // Cancel pending hung renderer checks since the renderer is responsive.
-  if (--in_flight_event_count_ == 0)
+  if (DecrementInFlightEventCount() == 0)
     StopHangMonitorTimeout();
 
   int type = static_cast<int>(event_type);