Eliminate ash::internal namespace

ash/system/tray/hover_highlight_view.h

Index: ash/system/tray/hover_highlight_view.h
diff --git a/ash/system/tray/hover_highlight_view.h b/ash/system/tray/hover_highlight_view.h
index 0ca9358f4674bd6755ff906062a40170c36fb2c9..17b50ba67e252b5ddd9f803e0f2136212e880c3e 100644
--- a/ash/system/tray/hover_highlight_view.h
+++ b/ash/system/tray/hover_highlight_view.h
@@ -15,8 +15,6 @@ class Label;
 }
 
 namespace ash {
-namespace internal {
-
 class ViewClickListener;
 
 // A view that changes background color on hover, and triggers a callback in the
@@ -87,7 +85,6 @@ class HoverHighlightView : public ActionableView {
   DISALLOW_COPY_AND_ASSIGN(HoverHighlightView);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_HOVER_HIGHLIGHT_VIEW_H_