Ensure the Chromoting Host process eventually terminates when shut down.

remoting/host/shutdown_watchdog.h

Index: remoting/host/shutdown_watchdog.h
diff --git a/remoting/host/shutdown_watchdog.h b/remoting/host/shutdown_watchdog.h
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+// Copyright 2014 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_SHUTDOWN_WATCHDOG_H_
+#define REMOTING_HOST_SHUTDOWN_WATCHDOG_H_
+
+#include "base/synchronization/lock.h"
+#include "base/threading/watchdog.h"
+
+namespace remoting {
+
+// This implements a watchdog timer that ensures the host process eventually
+// terminates, even if some threads are blocked or being kept alive for
+// some reason. This is not expected to trigger if host shutdown is working
+// correctly (on a normally loaded system). The triggering of the alarm
+// indicates a sign of trouble, and so the Alarm() method will log some
+// diagnostic information before shutting down the process.
+class ShutdownWatchdog : public base::Watchdog {
+ public:
+  // Creates a watchdog that waits for |duration| (after the watchdog is
+  // armed) before shutting down the process.
+  explicit ShutdownWatchdog(const base::TimeDelta& duration);
+
+  // This method should be called to set the process's exit-code before arming
+  // the watchdog. Otherwise an exit-code of 0 is assumed.
+  void SetExitCode(int exit_code);
+
+  void Alarm() override;
+
+ private:
+  int exit_code_;
+
+  // Protects |exit_code_|, since Alarm() gets called on a separate thread.
+  base::Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShutdownWatchdog);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_SHUTDOWN_WATCHDOG_H_