Move throttling of background timers into the renderer scheduler

components/scheduler/renderer/throttling_helper.h

Index: components/scheduler/renderer/throttling_helper.h
diff --git a/components/scheduler/renderer/throttling_helper.h b/components/scheduler/renderer/throttling_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..4513c097497dd9ee8b4000d56e722fc94d2e0310
--- /dev/null
+++ b/components/scheduler/renderer/throttling_helper.h
@@ -0,0 +1,64 @@
+// 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 COMPONENTS_SCHEDULER_RENDERER_THROTTLING_HELPER_H_
+#define COMPONENTS_SCHEDULER_RENDERER_THROTTLING_HELPER_H_
+
+#include <set>
+
+#include "base/macros.h"
+#include "components/scheduler/base/time_domain.h"
+#include "components/scheduler/scheduler_export.h"
+#include "third_party/WebKit/public/platform/WebViewScheduler.h"
+
+namespace scheduler {
+
+class RendererSchedulerImpl;
+class VirtualTimeDomain;
+class WebFrameSchedulerImpl;
+
+class SCHEDULER_EXPORT ThrottlingHelper : public TimeDomain::Observer {
+ public:
+  ThrottlingHelper(RendererSchedulerImpl* renderer_scheduler,
+                   const char* tracing_category);
+
+  ~ThrottlingHelper() override;
+
+  // TimeDomain::Observer implementation:
+  void OnRegisterAsUpdatableTaskQueue() override;
+  void OnRequestWakeup() override;
+
+  void ThrottleBackgroundFrame(WebFrameSchedulerImpl* frame_scheduler);

[Sami, 2015/11/24 12:48:48]

What if the unit that the ThrottlingHelper works with wasn't a
WebFrameSchedulerImpl but instead a TaskQueue? I think that way all the pumping
logic could live here and the frame scheduler would just need to add/remove the
timer queue here. WDYT?

[alex clarke (OOO till 29th), 2015/11/25 12:30:12]

Done.

[Sami, 2015/11/25 17:12:25]

Thanks, this seems like a nice simplification.

[alex clarke (OOO till 29th), 2015/11/26 18:43:27]

Acknowledged.

+  void UnthrottleForegroundFrame(WebFrameSchedulerImpl* frame_scheduler);
+  void Unregister(WebFrameSchedulerImpl* frame_scheduler);
+
+  const scoped_refptr<VirtualTimeDomain>& time_domain() const {
+    return time_domain_;
+  }
+
+  static base::TimeDelta DelayToNextRunTimeInSeconds(base::TimeTicks now);
+
+ private:
+  void PumpThrottledTasks();
+  void MaybeSchedulePumpThrottledTasksLocked();
+
+  std::set<WebFrameSchedulerImpl*> background_frame_schedulers_;
+  base::Closure pump_throttled_tasks_closure_;
+  RendererSchedulerImpl* renderer_scheduler_;  // NOT OWNED
+  const char* tracing_category_;               // NOT OWNED
+  scoped_refptr<VirtualTimeDomain> time_domain_;
+
+  // Protects members from the contigious block below.

[Sami, 2015/11/24 12:48:48]

typo: contiguous

[alex clarke (OOO till 29th), 2015/11/25 12:29:36]

Acknowledged.

+  base::Lock lock_;
+  bool pending_pump_throttled_tasks_;
+  bool work_to_do_;
+
+  base::WeakPtrFactory<ThrottlingHelper> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThrottlingHelper);
+};
+
+}  // namespace scheduler
+
+#endif  // COMPONENTS_SCHEDULER_RENDERER_THROTTLING_HELPER_H_