Eliminate ash::internal namespace

ash/wm/root_window_layout_manager.h

Index: ash/wm/root_window_layout_manager.h
diff --git a/ash/wm/root_window_layout_manager.h b/ash/wm/root_window_layout_manager.h
index 708e306b75b24b1e693cf303e85eb8031fbbe769..d9fd29757fe29ec7f94501803c0bb3f1eb0b55bf 100644
--- a/ash/wm/root_window_layout_manager.h
+++ b/ash/wm/root_window_layout_manager.h
@@ -25,7 +25,6 @@ class Widget;
 }
 
 namespace ash {
-namespace internal {
 
 // A layout manager for the root window.
 // Resizes all of its immediate children to fill the bounds of the root window.
@@ -50,7 +49,6 @@ class RootWindowLayoutManager : public aura::LayoutManager {
   DISALLOW_COPY_AND_ASSIGN(RootWindowLayoutManager);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_ROOT_WINDOW_LAYOUT_MANAGER_H_