Make rendering timeouts work even if paint data received early

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 17e3e82bff430ca29fc5826587cb998ecfb9a050..6843bea6313d4c1f4e45228046db4223ce069835 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -263,9 +263,11 @@ class CONTENT_EXPORT RenderWidgetHostImpl
   // a new compositor frame is not received before it expires.
   void StartNewContentRenderingTimeout();
 
-  // Stops the rendering timeout and prevents it from clearing any displayed
-  // graphics.
-  void StopNewContentRenderingTimeout();
+  // Notification that a new compositor frame has been generated following
+  // a page load. This stops |new_content_rendering_timeout_|, or prevents
+  // the timer from running if the load commit message hasn't been received
+  // yet.
+  void OnFirstPaintAfterLoad();
 
   // Forwards the given message to the renderer. These are called by the view
   // when it has received a message.
@@ -810,6 +812,11 @@ class CONTENT_EXPORT RenderWidgetHostImpl
   scoped_ptr<TimeoutMonitor> hang_monitor_timeout_;
 
   scoped_ptr<TimeoutMonitor> new_content_rendering_timeout_;
+  // This boolean is true if RenderWidgetHostImpl receives a compositor frame

[Charlie Reis, 2015/09/30 21:42:09]

nit: Add blank line above.

[kenrb, 2015/10/01 12:45:09]

Done.

+  // from a newly loaded page before OnFirstPaintAfterLoad() is called. In

[Charlie Reis, 2015/09/30 21:42:09]

Wait, that's not right.  It's true if the compositor frame is received (i.e.,
OnFirstPaintAfterLoad()) before commit (i.e.,
StartNewContentRenderingTimeout()).

Also, there's more things from my comment worth including here, like the fact it
gets reset at commit time and that these two IPCs arrive in a pair, not
interleaved with other navigations.

[kenrb, 2015/10/01 12:45:09]

Rewritten and expanded.

+  // that case |new_content_rendering_timeout_| is not needed, because the
+  // paint preceded the load commit notification.
+  bool received_paint_after_load_;
 
 #if defined(OS_WIN)
   std::list<HWND> dummy_windows_for_activation_;