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 e0dc39141dd57a1b24a7e2a85147cb5faa0cdd4a..35b8e85f9564d325c555bfef5e5aec5732d8281e 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"
@@ -151,6 +152,9 @@ class ASH_EXPORT SystemTray : public internal::ActionableView,
   // Returns true if the bubble exists.
   bool CloseBubbleForTest() const;
 
+  void SetShelfAlignment(ShelfAlignment alignment);
+  ShelfAlignment shelf_alignment() const { return shelf_alignment_; }
+
  private:
   friend class internal::SystemTrayLayerAnimationObserver;
   friend class internal::SystemTrayBubble;
@@ -240,6 +244,9 @@ 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>