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

remoting/host/it2me/it2me_host.h

Index: remoting/host/it2me/it2me_host.h
diff --git a/remoting/host/it2me/it2me_host.h b/remoting/host/it2me/it2me_host.h
index ba48cac5b0e232b2bbeaafe65995134c075aa1e2..ee4db8f6c70b0f3d771568ccfdd79488355c7ba0 100644
--- a/remoting/host/it2me/it2me_host.h
+++ b/remoting/host/it2me/it2me_host.h
@@ -35,6 +35,7 @@ class HostStatusLogger;
 class PolicyWatcher;
 class RegisterSupportHostRequest;
 class RsaKeyPair;
+class ScreenSaverBlocker;
 
 // These state values are duplicated in host_session.js and the Android Java
 // It2MeObserver class. Remember to update all copies when making changes.
@@ -156,6 +157,7 @@ class It2MeHost : public base::RefCountedThreadSafe<It2MeHost>,
   std::unique_ptr<HostStatusLogger> host_status_logger_;
   std::unique_ptr<DesktopEnvironmentFactory> desktop_environment_factory_;
   std::unique_ptr<HostEventLogger> host_event_logger_;
+  std::unique_ptr<ScreenSaverBlocker> screen_saver_blocker_;
 
   std::unique_ptr<ChromotingHost> host_;
   int failed_login_attempts_;