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

remoting/host/forward_process_stats_agent.h

Index: remoting/host/forward_process_stats_agent.h
diff --git a/remoting/host/forward_process_stats_agent.h b/remoting/host/forward_process_stats_agent.h
new file mode 100644
index 0000000000000000000000000000000000000000..9b3e3163f7ba94011b59332d7d690f090c594713
--- /dev/null
+++ b/remoting/host/forward_process_stats_agent.h
@@ -0,0 +1,31 @@
+// 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_FORWARD_PROCESS_STATS_AGENT_H_
+#define REMOTING_HOST_FORWARD_PROCESS_STATS_AGENT_H_
+
+#include "base/synchronization/lock.h"
+#include "remoting/host/process_stats_agent.h"
+#include "remoting/proto/process_stats.pb.h"
+
+namespace remoting {
+
+// A component to forward statistic data of another process.

[Sergey Ulanov, 2017/04/24 18:49:11]

I don't think this comment is clear and it doesn't match what this class
actually does. One might assume that this class talks to another process to get
stats, but it doesn't. Maybe reword it as follows:
// ProcessStatsAgent implementation that returns stats passed to 
// OnProcessStats(). Used to collect stats from processes other than 
// the current one.

[Hzj_jie, 2017/04/25 00:17:53]

Done.

+class ForwardProcessStatsAgent final : public ProcessStatsAgent {
+ public:
+  ForwardProcessStatsAgent();
+  ~ForwardProcessStatsAgent() override;
+
+  protocol::ProcessResourceUsage GetResourceUsage() override;
+
+  void OnProcessStats(const protocol::ProcessResourceUsage& usage);
+
+ private:
+  base::Lock lock_;

[Sergey Ulanov, 2017/04/24 18:49:11]

I don't think you need the lock. Normally all IPC messages are handled on the
network thread, so OnProcessStats() will be called on the same thread that calls
 GetResourceUsage().

[Hzj_jie, 2017/04/25 00:17:53]

Changed to ThreadChecker.

+  protocol::ProcessResourceUsage usage_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_FORWARD_PROCESS_STATS_AGENT_H_