Eliminate ash::internal namespace

ash/system/tray/system_tray_bubble.h

Index: ash/system/tray/system_tray_bubble.h
diff --git a/ash/system/tray/system_tray_bubble.h b/ash/system/tray/system_tray_bubble.h
index a8f576e83a3ac7452b552d0be98e40a45fabfacd..ece879c3b4d6a4e5a0579b3f734bc21f1b22a4bc 100644
--- a/ash/system/tray/system_tray_bubble.h
+++ b/ash/system/tray/system_tray_bubble.h
@@ -14,12 +14,9 @@
 #include <vector>
 
 namespace ash {
-
 class SystemTray;
 class SystemTrayItem;
 
-namespace internal {
-
 class SystemTrayBubble {
  public:
   enum BubbleType {
@@ -76,7 +73,6 @@ class SystemTrayBubble {
   DISALLOW_COPY_AND_ASSIGN(SystemTrayBubble);
 };
 
-}  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_BUBBLE_H_