Implement WebFrameScheduler and WebPageScheduler

components/scheduler/child/task_queue_manager.h

 // Copyright 2014 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.
 
 #ifndef CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
 #define CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
 
 #include <map>
 
 #include "base/atomic_sequence_num.h"
@@ skipping 70 matching lines @@
 
   // Returns true if any task from a monitored task queue was was run since the
   // last call to GetAndClearSystemIsQuiescentBit.
   bool GetAndClearSystemIsQuiescentBit();
 
   // Creates a task queue with the given |spec|.  Must be called on the thread
   // this class was created on.
   scoped_refptr<internal::TaskQueueImpl> NewTaskQueue(
       const TaskQueue::Spec& spec);
 
+  class SCHEDULER_EXPORT Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called when |queue| is unregistered.
+    virtual void OnUnregisterTaskQueue(
+        const scoped_refptr<internal::TaskQueueImpl>& queue) = 0;
+  };
+
+  // Called once to set the Observer. This function is called on the main
+  // thread. If |observer| is null, then no callbacks will occur.

[Sami, 2015/09/10 15:10:23]

nit: also mention the lifetime here.

[alex clarke (OOO till 29th), 2015/09/10 15:56:24]

Done.

+  void SetQueueObserver(Observer* observer);
+
  private:
   friend class internal::LazyNow;
   friend class internal::TaskQueueImpl;
   friend class TaskQueueManagerTest;
 
   class DeletionSentinel : public base::RefCounted<DeletionSentinel> {
    private:
     friend class base::RefCounted<DeletionSentinel>;
     ~DeletionSentinel() {}
   };
@@ skipping 123 matching lines @@
 
   int work_batch_size_;
 
   scoped_ptr<base::TickClock> time_source_;
 
   base::ObserverList<base::MessageLoop::TaskObserver> task_observers_;
 
   const char* disabled_by_default_tracing_category_;
   const char* disabled_by_default_verbose_tracing_category_;
 
+  Observer* queue_observer_;  // NOT OWNED
   scoped_refptr<DeletionSentinel> deletion_sentinel_;
   base::WeakPtrFactory<TaskQueueManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueManager);
 };
 
 }  // namespace scheduler
 
 #endif  // CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_