Prevent redundant DoWorks due to canceled delayed tasks

third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc

 // Copyright 2014 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.
 
 #include "platform/scheduler/base/task_queue_manager.h"
 
 #include <queue>
 #include <set>
 
 #include "base/bind.h"
@@ skipping 172 matching lines @@
   DCHECK_GE(delay, base::TimeDelta());
 
   // If there's a pending immediate DoWork then we rely on
   // TryAdvanceTimeDomains getting the TimeDomain to call
   // MaybeScheduleDelayedWork again when the immediate DoWork is complete.
   if (main_thread_pending_wakeups_.find(base::TimeTicks()) !=
       main_thread_pending_wakeups_.end()) {
     return;
   }
 
-  // De-duplicate DoWork posts.
+  // Only request the wake up if, either there are no wake ups scheduled, or if
+  // its sooner than any previously requested wake up.
   base::TimeTicks run_time = now + delay;
-  if (!main_thread_pending_wakeups_.insert(run_time).second)
+  if (!main_thread_pending_wakeups_.empty() &&
+      *main_thread_pending_wakeups_.begin() <= run_time) {
     return;
+  }
+  main_thread_pending_wakeups_.insert(run_time);
   delegate_->PostDelayedTask(
       from_here, base::Bind(&TaskQueueManager::DoWork,
                             weak_factory_.GetWeakPtr(), run_time, true),
       delay);
 }
 
 void TaskQueueManager::DoWork(base::TimeTicks run_time, bool from_main_thread) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   TRACE_EVENT1(tracing_category_, "TaskQueueManager::DoWork",
                "from_main_thread", from_main_thread);
@@ skipping 251 matching lines @@
   DCHECK(main_thread_checker_.CalledOnValidThread());
   DCHECK(!work_queue->Empty());
   if (observer_) {
     observer_->OnTriedToExecuteBlockedTask(*work_queue->task_queue(),
                                            *work_queue->GetFrontTask());
   }
 }
 
 }  // namespace scheduler
 }  // namespace blink