ash: Update launcher overflow chevron.

ash/launcher/launcher_view.h

Index: ash/launcher/launcher_view.h
diff --git a/ash/launcher/launcher_view.h b/ash/launcher/launcher_view.h
index 6dbe133e8a0946a884f47c3b49c4eebb383a5dda..f3102adc3e66d0bc587b0d4b7f722c5565ae18e9 100644
--- a/ash/launcher/launcher_view.h
+++ b/ash/launcher/launcher_view.h
@@ -20,7 +20,6 @@
 
 namespace views {
 class BoundsAnimator;
-class ImageButton;
 class MenuRunner;
 class ViewModel;
 }
@@ -42,6 +41,7 @@ class LauncherButton;
 class LauncherTooltipManager;
 class ShelfLayoutManager;
 class OverflowBubble;
+class OverflowButton;
 
 class ASH_EXPORT LauncherView : public views::View,
                                 public LauncherModelObserver,
@@ -238,7 +238,7 @@ class ASH_EXPORT LauncherView : public views::View,
 
   scoped_ptr<views::BoundsAnimator> bounds_animator_;
 
-  views::ImageButton* overflow_button_;
+  OverflowButton* overflow_button_;
 
   scoped_ptr<OverflowBubble> overflow_bubble_;