Report the duration of sampled tasks with histogram.

components/scheduler/renderer/task_duration_reporter.h

Index: components/scheduler/renderer/task_duration_reporter.h
diff --git a/components/scheduler/renderer/task_duration_reporter.h b/components/scheduler/renderer/task_duration_reporter.h
new file mode 100644
index 0000000000000000000000000000000000000000..8e9c528f2e746039a5e4ec8aafc457049f9bfbbc
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+++ b/components/scheduler/renderer/task_duration_reporter.h
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+// 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 COMPONENTS_SCHEDULER_RENDERER_TASK_DURATIN_REPORTER_H_
+#define COMPONENTS_SCHEDULER_RENDERER_TASK_DURATIN_REPORTER_H_
+
+#include "base/time/time.h"
+
+namespace scheduler {
+
+// Reports the task duration in a histogram for every 100th task. The histogram
+// ranges from 1 microsecond ~ 1 second with 100 bins. All tasks longer than 1
+// second will be put into the same bin.
+class TaskDurationReporter {
+ public:
+  TaskDurationReporter();
+  ~TaskDurationReporter();
+  void ReportTaskDuration(base::TimeDelta duration);
+
+ private:
+  int sample_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskDurationReporter);
+};
+}
+
+#endif  // COMPONENTS_SCHEDULER_RENDERER_TASK_DURATIN_REPORTER_H_