Eliminate ash::internal namespace

ash/drag_drop/drag_drop_tracker.h

Index: ash/drag_drop/drag_drop_tracker.h
diff --git a/ash/drag_drop/drag_drop_tracker.h b/ash/drag_drop/drag_drop_tracker.h
index b4dcf6e84bd882260c11c57e72b00b6663f65de1..670422b7dd2d208835394483539cd1387f466780 100644
--- a/ash/drag_drop/drag_drop_tracker.h
+++ b/ash/drag_drop/drag_drop_tracker.h
@@ -16,7 +16,6 @@ class WindowDelegate;
 }
 
 namespace ash {
-namespace internal {
 
 // Provides functions for handling drag events inside and outside the root
 // window where drag is started. This internally sets up a capture window for
@@ -53,7 +52,6 @@ class ASH_EXPORT DragDropTracker {
   DISALLOW_COPY_AND_ASSIGN(DragDropTracker);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_DRAG_DROP_DRAG_DROP_TRACKER_H_