Implement WebFrameScheduler and WebPageScheduler

components/scheduler/child/scheduler_helper.h

 // Copyright 2015 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 COMPONENTS_SCHEDULER_CHILD_SCHEDULER_HELPER_H_
 #define COMPONENTS_SCHEDULER_CHILD_SCHEDULER_HELPER_H_
 
 #include "components/scheduler/child/task_queue_manager.h"
 #include "components/scheduler/child/task_queue_selector.h"
 #include "components/scheduler/scheduler_export.h"
 
 namespace base {
 class TickClock;
 }
 
 namespace scheduler {
 
 class SchedulerTaskRunnerDelegate;
 
 // Common scheduler functionality for default tasks.
-class SCHEDULER_EXPORT SchedulerHelper {
+class SCHEDULER_EXPORT SchedulerHelper : public TaskQueueManager::Observer {
  public:
   // Category strings must have application lifetime (statics or
   // literals). They may not include " chars.
   SchedulerHelper(scoped_refptr<SchedulerTaskRunnerDelegate> main_task_runner,
                   const char* tracing_category,
                   const char* disabled_by_default_tracing_category,
                   const char* disabled_by_default_verbose_tracing_category);
-  ~SchedulerHelper();
+  ~SchedulerHelper() override;
+
+  // TaskQueueManager::Observer implementation:
+  void OnUnregisterTaskQueue(
+      const scoped_refptr<internal::TaskQueueImpl>& queue) override;
 
   // Returns the default task runner.
   scoped_refptr<TaskQueue> DefaultTaskRunner();
 
   // Returns the control task runner.  Tasks posted to this runner are executed
   // with the highest priority. Care must be taken to avoid starvation of other
   // task queues.
   scoped_refptr<TaskQueue> ControlTaskRunner();
 
   // Returns the control task after wakeup runner.  Tasks posted to this runner
@@ skipping 15 matching lines @@
   // Returns true if Shutdown() has been called. Otherwise returns false.
   bool IsShutdown() const { return !task_queue_manager_.get(); }
 
   void CheckOnValidThread() const {
     DCHECK(thread_checker_.CalledOnValidThread());
   }
 
   // Creates a new TaskQueue with the given |spec|.
   scoped_refptr<TaskQueue> NewTaskQueue(const TaskQueue::Spec& spec);
 
+  class SCHEDULER_EXPORT Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called when |queue| is unregistered.
+    virtual void OnUnregisterTaskQueue(
+        const scoped_refptr<TaskQueue>& 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: mention that the observer should outlive this class.

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

Done.

+  void SetQueueObserver(Observer* observer);
+
   // Accessor methods.
   base::TimeTicks Now() const;
   base::TimeTicks NextPendingDelayedTaskRunTime() const;
   bool GetAndClearSystemIsQuiescentBit();
 
   // Test helpers.
   void SetTimeSourceForTesting(scoped_ptr<base::TickClock> time_source);
   void SetWorkBatchSizeForTesting(size_t work_batch_size);
   TaskQueueManager* GetTaskQueueManagerForTesting();
 
  private:
   friend class SchedulerHelperTest;
 
   base::ThreadChecker thread_checker_;
   scoped_refptr<SchedulerTaskRunnerDelegate> main_task_runner_;
   scoped_ptr<TaskQueueManager> task_queue_manager_;
   scoped_refptr<TaskQueue> control_task_runner_;
   scoped_refptr<TaskQueue> control_after_wakeup_task_runner_;
   scoped_refptr<TaskQueue> default_task_runner_;
 
   scoped_ptr<base::TickClock> time_source_;
 
+  Observer* queue_observer_;  // NOT OWNED
   const char* tracing_category_;
   const char* disabled_by_default_tracing_category_;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerHelper);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_CHILD_SCHEDULER_HELPER_H_