Revert of [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 de227cc40f376a60f8b96c724160cf3e6c9f7efa..c57d23737a45a6631b7991d86b23c51ebe1f14ea 100644
--- a/third_party/WebKit/public/platform/scheduler/base/task_queue.h
+++ b/third_party/WebKit/public/platform/scheduler/base/task_queue.h
@@ -27,20 +27,6 @@ class BLINK_PLATFORM_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
  public:
   TaskQueue() {}
 
-  class BLINK_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|.
-    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;
@@ -164,7 +150,7 @@ class BLINK_PLATFORM_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
   // NOTE: this must be called on the thread this TaskQueue was created by.
   virtual bool HasPendingImmediateWork() const = 0;
 
-  // Returns requested run time of next scheduled wake-up for a delayed task
+  // Returns requested run time of next scheduled wakeup 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.
@@ -222,8 +208,6 @@ class BLINK_PLATFORM_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
 
   virtual bool BlockedByFence() const = 0;
 
-  virtual void SetObserver(Observer* observer) = 0;
-
  protected:
   ~TaskQueue() override {}