[scheduler] Add TaskQueue::Observer

third_party/WebKit/public/platform/scheduler/base/task_queue.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 THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_H_
 #define THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_H_
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/optional.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "public/platform/WebCommon.h"
 
 namespace base {
 namespace trace_event {
 class BlameContext;
 }
 }
 
 namespace blink {
 namespace scheduler {
 
 class TimeDomain;
 
 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;
 
   enum QueuePriority {
     // Queues with control priority will run before any other queue, and will
     // explicitly starve other queues. Typically this should only be used for
     // private queues which perform control operations.
     CONTROL_PRIORITY,
     // Queues with high priority will be selected preferentially over normal or
@@ skipping 161 matching lines @@
   // Note: delayed tasks get their enqueue order set once their delay has
   // expired, and non-delayed tasks get their enqueue order set when posted.
   virtual void InsertFence(InsertFencePosition position) = 0;
 
   // Removes any previously added fence and unblocks execution of any tasks
   // blocked by it.
   virtual void RemoveFence() = 0;
 
   virtual bool BlockedByFence() const = 0;
 
+  virtual void AddObserver(Observer* observer) = 0;
+  virtual void RemoveObserver(Observer* observer) = 0;
+
  protected:
   ~TaskQueue() override {}
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueue);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_H_