Eliminate ash::internal namespace

ash/wm/system_gesture_event_filter.h

Index: ash/wm/system_gesture_event_filter.h
diff --git a/ash/wm/system_gesture_event_filter.h b/ash/wm/system_gesture_event_filter.h
index 8fe82db65d3f4149d4c0a83bbf1188c38aa17bdd..43bf75853d7c9704d59f7bbdd6b273a21973afb4 100644
--- a/ash/wm/system_gesture_event_filter.h
+++ b/ash/wm/system_gesture_event_filter.h
@@ -9,16 +9,14 @@
 #include "ui/events/event_handler.h"
 
 namespace ash {
+class LongPressAffordanceHandler;
+class OverviewGestureHandler;
+class ShelfGestureHandler;
 
 namespace test {
 class SystemGestureEventFilterTest;
 }
 
-namespace internal {
-class LongPressAffordanceHandler;
-class OverviewGestureHandler;
-class ShelfGestureHandler;
-
 // An event filter which handles system level gesture events.
 class SystemGestureEventFilter : public ui::EventHandler {
  public:
@@ -41,7 +39,6 @@ class SystemGestureEventFilter : public ui::EventHandler {
   DISALLOW_COPY_AND_ASSIGN(SystemGestureEventFilter);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_SYSTEM_GESTURE_EVENT_FILTER_H_