Revert of [scheduler] Change TaskQueue observer call mechanism.

third_party/WebKit/Source/platform/scheduler/base/time_domain.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_TIME_DOMAIN_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TIME_DOMAIN_H_
 
 #include <map>
 
 #include "base/callback.h"
@@ skipping 117 matching lines @@
 
     void SetHeapHandle(HeapHandle handle) {
       DCHECK(handle.IsValid());
       queue->set_heap_handle(handle);
     }
 
     void ClearHeapHandle() {
       DCHECK(queue->heap_handle().IsValid());
       queue->set_heap_handle(HeapHandle());
 
-      DCHECK(queue->scheduled_time_domain_wake_up());
-      queue->SetScheduledTimeDomainWakeUp(base::nullopt);
+      DCHECK_NE(queue->scheduled_time_domain_wake_up(), base::TimeTicks());
+      queue->set_scheduled_time_domain_wake_up(base::TimeTicks());
     }
   };
 
   IntrusiveHeap<ScheduledDelayedWakeUp> delayed_wake_up_queue_;
 
   base::ThreadChecker main_thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(TimeDomain);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TIME_DOMAIN_H_