chromeos: Request screen lock directly from session manager.

chrome/browser/chromeos/power/power_button_observer.h

Index: chrome/browser/chromeos/power/power_button_observer.h
diff --git a/chrome/browser/chromeos/power/power_button_observer.h b/chrome/browser/chromeos/power/power_button_observer.h
index 6cbd402bafcea77063d8eefae28a6dd9713afc36..b1dfca9967eae475ca4bf147264c343197cc2ecb 100644
--- a/chrome/browser/chromeos/power/power_button_observer.h
+++ b/chrome/browser/chromeos/power/power_button_observer.h
@@ -9,6 +9,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "chromeos/dbus/power_manager_client.h"
+#include "chromeos/dbus/session_manager_client.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
@@ -17,7 +18,8 @@ namespace chromeos {
 // Listens for power button, login, and screen lock events and passes them to
 // the Aura shell's PowerButtonController class.
 class PowerButtonObserver : public content::NotificationObserver,
-                            public PowerManagerClient::Observer {
+                            public PowerManagerClient::Observer,
+                            public SessionManagerClient::Observer {
  public:
   // This class registers/unregisters itself as an observer in ctor/dtor.
   PowerButtonObserver();
@@ -34,6 +36,8 @@ class PowerButtonObserver : public content::NotificationObserver,
       bool down, const base::TimeTicks& timestamp) OVERRIDE;
   virtual void LockButtonStateChanged(
       bool down, const base::TimeTicks& timestamp) OVERRIDE;
+
+  // SessionManagerClient::Observer implementation.
   virtual void LockScreen() OVERRIDE;
 
   content::NotificationRegistrar registrar_;