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..a7eaab7057f9e5ac95bc1d4cd1bb6b10f04d68e0
--- /dev/null
+++ b/components/scheduler/renderer/task_duration_reporter.h
@@ -0,0 +1,26 @@
+// 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 {
+
+// Report the task duration in a histogram for every 100th task

[majidvp, 2016/07/27 18:34:03]

nit: comment should end with a period.

[sunyunjia, 2016/07/27 19:51:04]

Done.

+class TaskDurationReporter {
+ public:
+  TaskDurationReporter();
+  ~TaskDurationReporter();
+  void ReportSampleDuration(base::TimeDelta duration);

[tdresser, 2016/07/27 18:04:25]

Maybe ReportTaskDuration?

[sunyunjia, 2016/07/27 19:51:04]

Done.

+ private:
+  int sample_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskDurationReporter);
+};
+
+}
+
+#endif // COMPONENTS_SCHEDULER_RENDERER_TASK_DURATIN_REPORTER_H_