[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, it starts immediately
+// after construction, and stops before destruction.

[joedow, 2017/04/26 23:48:02]

s/before/after

The class stops when the d'tor is called, but I don't think it stops beforehand.

[Hzj_jie, 2017/04/27 02:21:34]

Done.

+// 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 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();
+
+  // Add a new ProcessStatsAgent. Users should call this function at least once
+  // immediately after constructor in the same thread.
+  void AddProcessStatsAgent(std::unique_ptr<ProcessStatsAgent> agent);
+
+ private:
+  void ReportUsage();
+
+  protocol::ProcessStatsStub* const host_stats_stub_;
+  std::vector<std::unique_ptr<ProcessStatsAgent>> agents_;
+  base::RepeatingTimer timer_;
+  const base::ThreadChecker thread_checker_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_PROCESS_STATS_SENDER_H_