[scheduler] Add TaskQueue::Observer

third_party/WebKit/public/platform/scheduler/base/task_queue.h

Index: third_party/WebKit/public/platform/scheduler/base/task_queue.h
diff --git a/third_party/WebKit/public/platform/scheduler/base/task_queue.h b/third_party/WebKit/public/platform/scheduler/base/task_queue.h
index c57d23737a45a6631b7991d86b23c51ebe1f14ea..64d9d35112d56e7f2ed1b3fcbcc721e3cb6c8380 100644
--- a/third_party/WebKit/public/platform/scheduler/base/task_queue.h
+++ b/third_party/WebKit/public/platform/scheduler/base/task_queue.h
@@ -27,6 +27,17 @@ class BLINK_PLATFORM_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
  public:
   TaskQueue() {}
 
+  class BLINK_PLATFORM_EXPORT Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Notify observer that wakeup has changed. |next_wakeup| can be in the
+    // past (e.g. base::TimeTicks() can be used to notify about immediate
+    // work.

[Sami, 2017/04/04 19:07:30]

Mention which thread this is called on.

[Sami, 2017/04/05 11:24:00]

Also, did we wanna specify which functions can be called in the callback (or is
it now everything except for adding/removing observers?)

[altimin, 2017/04/05 11:35:58]

Done.

[altimin, 2017/04/05 11:35:58]

Done.

+    virtual void OnQueueNextWakeupChanged(TaskQueue* queue,
+                                          base::TimeTicks next_wakeup) = 0;
+  };
+
   // Unregisters the task queue after which no tasks posted to it will run and
   // the TaskQueueManager's reference to it will be released soon.
   virtual void UnregisterTaskQueue() = 0;
@@ -208,6 +219,9 @@ class BLINK_PLATFORM_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
 
   virtual bool BlockedByFence() const = 0;
 
+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
+
  protected:
   ~TaskQueue() override {}