chromeos: Remove old LockScreen signal.

chromeos/dbus/session_manager_client.h

Index: chromeos/dbus/session_manager_client.h
diff --git a/chromeos/dbus/session_manager_client.h b/chromeos/dbus/session_manager_client.h
index c803f2f2ce08f101009d37b60f1e59acefe1f9d2..69a4d3647c65812de6ef4b6d83dbc670c44a5d14 100644
--- a/chromeos/dbus/session_manager_client.h
+++ b/chromeos/dbus/session_manager_client.h
@@ -28,14 +28,6 @@ class CHROMEOS_EXPORT SessionManagerClient : public DBusClient {
     // Called when the property change is complete.
     virtual void PropertyChangeComplete(bool success) {}
 
-    // Called when the session manager requests that the lock screen be
-    // displayed.  NotifyLockScreenShown() is called after the lock screen
-    // is shown (the canonical "is the screen locked?" state lives in the
-    // session manager).
-    // TODO(derat): Delete this once the session manager is calling the
-    // "LockScreen" method instead.
-    virtual void LockScreen() {}
-
     // Called when the session manager announces that the screen has been locked
     // successfully (i.e. after NotifyLockScreenShown() has been called).
     virtual void ScreenIsLocked() {}