[Chromoting] Use device::PowerSaveBlocker to block screen saver

remoting/host/screen_saver_blocker.h

Index: remoting/host/screen_saver_blocker.h
diff --git a/remoting/host/screen_saver_blocker.h b/remoting/host/screen_saver_blocker.h
new file mode 100644
index 0000000000000000000000000000000000000000..48f8914587dd95bed1e91fcc1377edb8c8d2057e
--- /dev/null
+++ b/remoting/host/screen_saver_blocker.h
@@ -0,0 +1,40 @@
+// Copyright 2016 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_SCREEN_SAVER_BLOCKER_H_
+#define REMOTING_HOST_SCREEN_SAVER_BLOCKER_H_
+
+#include <memory>
+#include <string>
+
+#include "base/memory/weak_ptr.h"
+#include "device/power_save_blocker/power_save_blocker.h"
+#include "remoting/host/chromoting_host_context.h"
+#include "remoting/host/host_status_observer.h"
+
+namespace remoting {
+
+class HostStatusMonitor;
+
+// A HostStatusObserver to block screen saver from taking effect during the
+// lifetime of a remoting connection.
+class ScreenSaverBlocker : public HostStatusObserver {

[Sergey Ulanov, 2016/07/08 21:31:47]

I don't think this is the best name, as it blocks sleep as well, not only screen
saver. Call it HostPowerSaveBlocker?

[Hzj_jie, 2016/07/10 22:04:57]

Indeed blocking screensaver implies the suspending should also be blocked. Since
a hardware cannot display when it suspended. So
PowerSaveBlocker::kPowerSaveBlockPreventDisplaySleep implies
kPowerSaveBlockPreventAppSuspension. But I have no strong feeling about this
naming. Updated.

+ public:
+  ScreenSaverBlocker(base::WeakPtr<HostStatusMonitor> monitor,
+                     std::unique_ptr<ChromotingHostContext>&& context);

[Sergey Ulanov, 2016/07/08 21:31:47]

Please pass unique_ptr by value instead of rvalue. But in this case we shouldn't
be passing context ownership at all. Instead I suggest passing task runners for
the UI and file threads.

[Hzj_jie, 2016/07/10 22:04:57]

Done.

+
+  ~ScreenSaverBlocker() override;
+
+  void OnClientConnected(const std::string& jid) override;
+  void OnClientDisconnected(const std::string& jid) override;
+
+ private:
+  base::WeakPtr<HostStatusMonitor> monitor_;
+  std::unique_ptr<ChromotingHostContext> context_;
+  std::unique_ptr<device::PowerSaveBlocker> blocker_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_SCREEN_SAVER_BLOCKER_H_