Remove after wakeup logic and replace PumpTask with Fences

third_party/WebKit/Source/platform/scheduler/renderer/throttling_helper.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_RENDERER_THROTTLING_HELPER_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_THROTTLING_HELPER_H_
 
 #include <set>
 
 #include "base/macros.h"
 #include "platform/scheduler/base/cancelable_closure_holder.h"
 #include "platform/scheduler/base/time_domain.h"
 #include "public/platform/WebViewScheduler.h"
 
 namespace blink {
 namespace scheduler {
 
 class RendererSchedulerImpl;
 class ThrottledTimeDomain;
 class WebFrameSchedulerImpl;
 
+// The job of the ThrottlingHelper is to run tasks posted on throttled queues at
+// most once per second. This is done by disabling throttled queues and running
+// a special "heart beat" function |PumpThrottledTasks| which when run
+// temporarily enables throttled queues and inserts a fence to ensure tasks
+// posted from a throttled task run next time the queue is pumped.
+//
+// Of course the ThrottlingHelper isn't the only sub-system that wants to enable
+// or disable queues. E.g. RendererSchedulerImpl also does this for policy
+// reasons.  To prevent the systems from fighting, clients of ThrottlingHelper
+// must use SetQueueEnabled rather than calling the function directly on the
+// queue.
+//
+// There may be more than one system that wishes to throttle a queue (e.g.
+// renderer suspension vs tab level suspension) so the ThrottlingHelper keeps a
+// count of the number of systems that wish a queue to be throttled.
+// See IncreaseThrottleRefCount & DecreaseThrottleRefCount.
 class BLINK_PLATFORM_EXPORT ThrottlingHelper : public TimeDomain::Observer {
  public:
   ThrottlingHelper(RendererSchedulerImpl* renderer_scheduler,
                    const char* tracing_category);
 
   ~ThrottlingHelper() override;
 
   // TimeDomain::Observer implementation:
   void OnTimeDomainHasImmediateWork() override;
   void OnTimeDomainHasDelayedWork() override;
@@ skipping 11 matching lines @@
   void IncreaseThrottleRefCount(TaskQueue* task_queue);
 
   // If the refcouint is non-zero it's decremented.  If the throttled refcount
   // becomes zero then |task_queue| is unthrottled.  If the refcount was already
   // zero this function does nothing.
   void DecreaseThrottleRefCount(TaskQueue* task_queue);
 
   // Removes |task_queue| from |throttled_queues_|.
   void UnregisterTaskQueue(TaskQueue* task_queue);
 
+  // Returns true if the |task_queue| is throttled.
+  bool IsThrottled(TaskQueue* task_queue) const;
+
   // Tells the ThrottlingHelper we're using virtual time, which disables all
   // throttling.
   void EnableVirtualTime();
 
   const ThrottledTimeDomain* time_domain() const { return time_domain_.get(); }
 
   static base::TimeTicks ThrottledRunTime(base::TimeTicks unthrottled_runtime);
 
   const scoped_refptr<TaskQueue>& task_runner() const { return task_runner_; }
 
@@ skipping 33 matching lines @@
 
   base::WeakPtrFactory<ThrottlingHelper> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ThrottlingHelper);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_THROTTLING_HELPER_H_