[Chromoting] Retrieve process resource usage (ProcessStats) and its tests

remoting/host/process_stats_sender.h

+// Copyright 2017 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 REMOTING_HOST_PROCESS_STATS_SENDER_H_
+#define REMOTING_HOST_PROCESS_STATS_SENDER_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/threading/thread_checker.h"
+#include "base/time/time.h"
+#include "base/timer/timer.h"
+#include "remoting/proto/process_stats.pb.h"
+#include "remoting/protocol/process_stats_stub.h"
+
+namespace remoting {
+
+class ProcessStatsAgent;
+
+// A component to report process statistic data regularly.
+// All public functions, including constructor and destructor of the object of
+// ProcessStatsSender need to be executed in a same thread.
+class ProcessStatsSender final {
+ public:
+  // ProcessStatsSender starts immediately and reports statistic data to
+  // |host_stats_stub| once per |interval|.
+  // ProcessStatsSender does not take the ownership of |host_stats_stub|. It
+  // must outlive the ProcessStatsSender object.
+  ProcessStatsSender(protocol::ProcessStatsStub* host_stats_stub,
+                     base::TimeDelta interval);
+
+  // ProcessStatsSender stops in destruction.

[joedow, 2017/04/26 16:44:06]

I don't think this comment is needed (most classes stop doing things when they
are destroyed).  If it is important for usage of the calss, you can move it into
the class documentation but I think it is safe to delete.

[Hzj_jie, 2017/04/26 20:47:19]

I have moved the comments regarding to the time of starting and stopping all
into the class documentation.
Done.

+  ~ProcessStatsSender();
+
+  void AddProcessStatsAgent(std::unique_ptr<ProcessStatsAgent> agent);
+
+ private:
+  void ReportUsage();
+
+  protocol::ProcessStatsStub* const host_stats_stub_;
+  const base::TimeDelta interval_;

[Sergey Ulanov, 2017/04/26 05:42:44]

I don't think you need this field. The constructor can just pass interval
parameter to the timer_

[Hzj_jie, 2017/04/26 20:47:19]

Oh, yes, that's for the old Start() and Stop() design.

+  std::vector<std::unique_ptr<ProcessStatsAgent>> agents_;
+  base::RepeatingTimer timer_;
+  const base::ThreadChecker thread_checker_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_PROCESS_STATS_SENDER_H_