Handles the failures of output state change.

chromeos/display/output_configurator.h

Index: chromeos/display/output_configurator.h
diff --git a/chromeos/display/output_configurator.h b/chromeos/display/output_configurator.h
index 1b9746f4394bc7712be544ca4774f1a218ea28c1..4e2b10e37fe58a5e0324a6aeee2301a864d7119a 100644
--- a/chromeos/display/output_configurator.h
+++ b/chromeos/display/output_configurator.h
@@ -48,7 +48,10 @@ class CHROMEOS_EXPORT OutputConfigurator : public MessageLoop::Dispatcher {
    public:
     // Called when the change of the display mode finished.  It will usually
     // start the fading in the displays.
-    virtual void OnDisplayModeChanged() = 0;
+    virtual void OnDisplayModeChanged() {};
+
+    // Called when the change of the display mode is issued but failed.
+    virtual void OnDisplayModeChangeFailed() {};
   };
 
   OutputConfigurator();