Eliminate ash::internal namespace

ash/system/chromeos/tray_display.h

Index: ash/system/chromeos/tray_display.h
diff --git a/ash/system/chromeos/tray_display.h b/ash/system/chromeos/tray_display.h
index e111d7d4823837a1ffedb0ce731ca762b70e7b48..fc01ba2f7c9128f6f8fe4bd86c02decba6b2807a 100644
--- a/ash/system/chromeos/tray_display.h
+++ b/ash/system/chromeos/tray_display.h
@@ -15,13 +15,12 @@
 #include "ui/views/view.h"
 
 namespace ash {
+class DisplayView;
+
 namespace test {
 class AshTestBase;
 }
 
-namespace internal {
-class DisplayView;
-
 class ASH_EXPORT TrayDisplay : public SystemTrayItem,
                                public DisplayController::Observer {
  public:
@@ -74,7 +73,6 @@ class ASH_EXPORT TrayDisplay : public SystemTrayItem,
   DISALLOW_COPY_AND_ASSIGN(TrayDisplay);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_TRAY_DISPLAY_H_