[Reland] Make canceling Timers fast.

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

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
index f44ee457a87e5189ddb438b495d6db1920f95be9..7d1ffda8d72983e0d51f923bc25f0f910c8ca177 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
@@ -275,19 +275,24 @@ TaskQueueManager::ProcessTaskResult TaskQueueManager::ProcessTaskFromWorkQueue(
     internal::WorkQueue* work_queue) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   scoped_refptr<DeletionSentinel> protect(deletion_sentinel_);
-  internal::TaskQueueImpl* queue = work_queue->task_queue();
+  internal::TaskQueueImpl::Task pending_task =
+      work_queue->TakeTaskFromWorkQueue();
+
+  // It's possible the task was canceled, if so bail out.
+  if (pending_task.task.IsCancelled())
+    return ProcessTaskResult::EXECUTED;
 
+  internal::TaskQueueImpl* queue = work_queue->task_queue();
   if (queue->GetQuiescenceMonitored())
     task_was_run_on_quiescence_monitored_queue_ = true;
 
-  internal::TaskQueueImpl::Task pending_task =
-      work_queue->TakeTaskFromWorkQueue();
   if (!pending_task.nestable && delegate_->IsNested()) {
     // Defer non-nestable work to the main task runner.  NOTE these tasks can be
     // arbitrarily delayed so the additional delay should not be a problem.
     // TODO(skyostil): Figure out a way to not forget which task queue the
     // task is associated with. See http://crbug.com/522843.
-    delegate_->PostNonNestableTask(pending_task.posted_from, pending_task.task);
+    delegate_->PostNonNestableTask(pending_task.posted_from,
+                                   std::move(pending_task.task));
     return ProcessTaskResult::DEFERRED;
   }