ash: Cleanup class/struct forward declarations

ash/display/resolution_notification_controller.h

Index: ash/display/resolution_notification_controller.h
diff --git a/ash/display/resolution_notification_controller.h b/ash/display/resolution_notification_controller.h
index 3eed4bf9cfa726fa6026524bc99d3357e85c6be7..8ac70473323293d1bb03ea4661039c57e0916c18 100644
--- a/ash/display/resolution_notification_controller.h
+++ b/ash/display/resolution_notification_controller.h
@@ -20,15 +20,8 @@ namespace chromeos {
 FORWARD_DECLARE_TEST(DisplayPreferencesTest, PreventStore);
 }  // namespace chromeos
 
-namespace views {
-class Label;
-class Widget;
-}  // namespace views
-
 namespace ash {
 
-class DisplayMode;
-
 // A class which manages the notification of display resolution change and
 // also manages the timeout in case the new resolution is unusable.
 class ASH_EXPORT ResolutionNotificationController