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

remoting/host/process_stats_agent.h

Index: remoting/host/process_stats_agent.h
diff --git a/remoting/host/process_stats_agent.h b/remoting/host/process_stats_agent.h
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+// 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_AGENT_H_
+#define REMOTING_HOST_PROCESS_STATS_AGENT_H_
+
+#include "remoting/proto/process_stats.pb.h"
+
+namespace remoting {
+
+// An interface to report the process statistic data.
+class ProcessStatsAgent {
+ public:
+  ProcessStatsAgent() = default;
+  virtual ~ProcessStatsAgent() = default;
+
+  // This function is expected to be executed in an IO-disallowed thread: if the
+  // implementation requires IO access or may cost a significant amount of time,
+  // using a background thread is preferred.
+  virtual protocol::ProcessResourceUsage GetResourceUsage() = 0;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_PROCESS_STATS_AGENT_H_