scheduler: Implement task observers

content/renderer/scheduler/renderer_scheduler.h

Index: content/renderer/scheduler/renderer_scheduler.h
diff --git a/content/renderer/scheduler/renderer_scheduler.h b/content/renderer/scheduler/renderer_scheduler.h
index 6b4ecfaceef4fcd45bd998c5d288eed43c650371..ada8a94319a15267d11f82eee6c5912cd9f397b4 100644
--- a/content/renderer/scheduler/renderer_scheduler.h
+++ b/content/renderer/scheduler/renderer_scheduler.h
@@ -71,6 +71,12 @@ class CONTENT_EXPORT RendererScheduler {
   // silently dropped.
   virtual void Shutdown() = 0;
 
+  // These functions can only be called on the main thread.

[rmcilroy, 2015/02/13 12:53:21]

nit - could you add a comment to explain when the task observer will be
triggered.

[Sami, 2015/02/13 14:27:26]

Sure thing, this comment was just copied verbatim from MessageLoop.

+  virtual void AddTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;
+  virtual void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;

[rmcilroy, 2015/02/13 12:53:21]

nit - move above Shutdown()

[Sami, 2015/02/13 14:27:26]

Done.

+
  protected:
   RendererScheduler();
   DISALLOW_COPY_AND_ASSIGN(RendererScheduler);