Revert of [scheduler] Change TaskQueue observer call mechanism.

third_party/WebKit/Source/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_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_H_
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/optional.h"
@@ skipping 19 matching lines @@
   class PLATFORM_EXPORT Observer {
    public:
     virtual ~Observer() {}
 
     // Notify observer that the time at which this queue wants to run
     // the next task has changed. |next_wakeup| can be in the past
     // (e.g. base::TimeTicks() can be used to notify about immediate work).
     // Can be called on any thread
     // All methods but SetObserver, SetTimeDomain and GetTimeDomain can be
     // called on |queue|.
-    //
-    // TODO(altimin): Make it base::Optional<base::TimeTicks> to tell
-    // observer about cancellations.
     virtual void OnQueueNextWakeUpChanged(TaskQueue* queue,
                                           base::TimeTicks next_wake_up) = 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
@@ skipping 105 matching lines @@
   virtual bool IsQueueEnabled() const = 0;
 
   // Returns true if the queue is completely empty.
   virtual bool IsEmpty() const = 0;
 
   // Returns the number of pending tasks in the queue.
   virtual size_t GetNumberOfPendingTasks() const = 0;
 
   // Returns true if the queue has work that's ready to execute now.
   // NOTE: this must be called on the thread this TaskQueue was created by.
-  virtual bool HasTaskToRunImmediately() const = 0;
+  virtual bool HasPendingImmediateWork() const = 0;
 
   // Returns requested run time of next scheduled wake-up for a delayed task
   // which is not ready to run. If there are no such tasks or the queue is
   // disabled (by a QueueEnabledVoter) it returns base::nullopt.
   // NOTE: this must be called on the thread this TaskQueue was created by.
   virtual base::Optional<base::TimeTicks> GetNextScheduledWakeUp() = 0;
 
   // Can be called on any thread.
   virtual QueueType GetQueueType() const = 0;
 
@@ skipping 54 matching lines @@
  protected:
   ~TaskQueue() override {}
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueue);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_H_