[scheduler] Monitor renderer load level.

third_party/WebKit/Source/platform/scheduler/renderer/renderer_load_tracker.h

+// Copyright 2016 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_RENDERER_LOAD_TRACKER_H_
+#define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_RENDERER_LOAD_TRACKER_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/time/time.h"
+#include "public/platform/WebCommon.h"
+
+namespace blink {
+namespace scheduler {
+
+// This class tracks renderer load level.

[Sami, 2016/08/22 14:33:16]

nit: This comment basically just repeats the class name :) How about also
explaining what load level means?

[altimin, 2016/08/22 15:36:24]

Done.

+// In order to avoid bias it reports load level at regular intervals.
+class BLINK_PLATFORM_EXPORT RendererLoadTracker {

[Sami, 2016/08/22 14:33:16]

Since this only tracks the main thread instead of the whole renderer, should we
call this something like ThreadLoadTracker? (And also move it next to the other
estimators in ../base)

[altimin, 2016/08/22 15:36:24]

Done.

+ public:
+  // Callback is called with (current_time, load_level) parameters.
+  using Callback = base::Callback<void(base::TimeTicks, double)>;
+
+  RendererLoadTracker(base::TimeTicks now, const Callback& callback);
+  ~RendererLoadTracker();
+
+  void Pause(base::TimeTicks now);
+  void Resume(base::TimeTicks now);
+
+  void RecordTaskTime(base::TimeTicks start_time, base::TimeTicks end_time);
+
+  void RecordIdle(base::TimeTicks now);

[Sami, 2016/08/22 14:33:16]

Could we also count wake-ups here? Could you add a TODO for that?

[altimin, 2016/08/22 15:36:23]

Done.

+
+ private:
+  void Advance(base::TimeTicks now, bool is_active, bool is_task_running);
+
+  double Load();
+
+  base::TimeTicks current_time_;
+  base::TimeTicks next_reporting_time_;
+
+  bool active_;
+  base::TimeTicks last_status_change_time_;
+
+  base::TimeDelta total_time_;
+  base::TimeDelta total_runtime_;
+
+  // Start reporting values after |waiting_period_|.
+  base::TimeDelta waiting_period_;
+  base::TimeDelta reporting_interval_;
+
+  Callback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(RendererLoadTracker);
+};
+
+}  // namespace scheduler
+}  // namespace blink
+
+#endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_RENDERER_LOAD_TRACKER_H_