Use the correct launcher assets for shelf alignment.

ash/launcher/overflow_button.h

Index: ash/launcher/overflow_button.h
diff --git a/ash/launcher/overflow_button.h b/ash/launcher/overflow_button.h
index be24ba61575444aa3a194e5176a473361db149ec..69cc79592d3a6541a2204fe210a2392d6a511adb 100644
--- a/ash/launcher/overflow_button.h
+++ b/ash/launcher/overflow_button.h
@@ -23,7 +23,7 @@ class OverflowButton : public views::CustomButton {
   explicit OverflowButton(views::ButtonListener* listener);
   virtual ~OverflowButton();
 
-  void SetShelfAlignment(ShelfAlignment alignment);
+  void OnShelfAlignmentChanged();
 
  private:
   void PaintBackground(gfx::Canvas* canvas, int alpha);
@@ -31,7 +31,6 @@ class OverflowButton : public views::CustomButton {
   // views::View overrides:
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
 
-  ShelfAlignment alignment_;
   const gfx::ImageSkia* image_;
 
   DISALLOW_COPY_AND_ASSIGN(OverflowButton);