Add left/right layout support for uber tray.

ash/system/tray/system_tray.h

Index: ash/system/tray/system_tray.h
diff --git a/ash/system/tray/system_tray.h b/ash/system/tray/system_tray.h
index 24e8257e3ef94eaddda38f23ea5fc1d267c9417d..129179f1235a683da259fe9ee873162264564fd5 100644
--- a/ash/system/tray/system_tray.h
+++ b/ash/system/tray/system_tray.h
@@ -10,6 +10,7 @@
 #include "ash/ash_export.h"
 #include "ash/system/tray/tray_views.h"
 #include "ash/system/user/login_status.h"
+#include "ash/wm/shelf_auto_hide_behavior.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
@@ -144,6 +145,9 @@ class ASH_EXPORT SystemTray : public internal::ActionableView,
   // Returns true if the bubble exists.
   bool CloseBubbleForTest() const;
 
+  void SetAlignment(ShelfAlignment alignment);
+  ShelfAlignment GetAlignment() const;
+
  private:
   friend class internal::SystemTrayLayerAnimationObserver;
   friend class internal::SystemTrayBubble;
@@ -229,6 +233,9 @@ class ASH_EXPORT SystemTray : public internal::ActionableView,
   // See description agove getter.
   bool should_show_launcher_;
 
+  // Shelf alignment.
+  ShelfAlignment shelf_alignment_;
+
   internal::BackgroundAnimator hide_background_animator_;
   internal::BackgroundAnimator hover_background_animator_;
   scoped_ptr<internal::SystemTrayLayerAnimationObserver>