Prevent hang monitor restarts when hidden

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 846 matching lines @@
   // Send out a request to the renderer to paint the view if required.
   repaint_start_time_ = TimeTicks::Now();
   repaint_ack_pending_ = true;
   TRACE_EVENT_ASYNC_BEGIN0(
       "renderer_host", "RenderWidgetHostImpl::repaint_ack_pending_", this);
   Send(new ViewMsg_Repaint(routing_id_, current_size_));
   return true;
 }
 
 void RenderWidgetHostImpl::StartHangMonitorTimeout(base::TimeDelta delay) {
+  if (is_hidden_)
+    return;

[piman, 2015/02/19 23:43:52]

Do we need to restart it when we go visible (i.e. keep around the state that we
want it running), or does it not matter?

[jdduke (slow), 2015/02/23 16:03:26]

Good question, and I don't really have the answer. I think ideally the answer is
yes, but this change is simply making our decision to turn the timeout off
consistent when the widget is hidden.

I'm a little hesitant to make that behavior change now, given how fragile this
has been, but I think we should look into it. I'll file a bug and note it here.

   if (hang_monitor_timeout_)
     hang_monitor_timeout_->Start(delay);
 }
 
 void RenderWidgetHostImpl::RestartHangMonitorTimeout() {
+  if (is_hidden_)
+    return;
   if (hang_monitor_timeout_)
     hang_monitor_timeout_->Restart(
         base::TimeDelta::FromMilliseconds(hung_renderer_delay_ms_));
 }
 
 void RenderWidgetHostImpl::StopHangMonitorTimeout() {
   if (hang_monitor_timeout_)
     hang_monitor_timeout_->Stop();
   RendererIsResponsive();
 }
@@ skipping 1315 matching lines @@
 }
 #endif
 
 SkColorType RenderWidgetHostImpl::PreferredReadbackFormat() {
   if (view_)
     return view_->PreferredReadbackFormat();
   return kN32_SkColorType;
 }
 
 }  // namespace content