Eliminate ash::internal namespace

ash/display/mirror_window_controller.h

Index: ash/display/mirror_window_controller.h
diff --git a/ash/display/mirror_window_controller.h b/ash/display/mirror_window_controller.h
index c70e9d8a211897ebd2f17012c5c19a2c45997926..89b2b61c036255024925bf88fda0dfa20fb79f18 100644
--- a/ash/display/mirror_window_controller.h
+++ b/ash/display/mirror_window_controller.h
@@ -26,13 +26,12 @@ class Reflector;
 }
 
 namespace ash {
+class DisplayInfo;
+
 namespace test{
 class MirrorWindowTestApi;
 }
 
-namespace internal {
-class DisplayInfo;
-
 // An object that copies the content of the primary root window to a
 // mirror window. This also draws a mouse cursor as the mouse cursor
 // is typically drawn by the window system.
@@ -71,7 +70,6 @@ class ASH_EXPORT MirrorWindowController : public aura::WindowTreeHostObserver {
   DISALLOW_COPY_AND_ASSIGN(MirrorWindowController);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_DISPLAY_MIRROR_WINDOW_CONTROLLER_H_