Add pretargethandler to exit overview mode on touch/click.

ash/desktop_background/desktop_background_view.h

Index: ash/desktop_background/desktop_background_view.h
diff --git a/ash/desktop_background/desktop_background_view.h b/ash/desktop_background/desktop_background_view.h
index c25f9d9bff9acdb5850c09178729dab069ff6a65..8a598f3d3a77546357bc7929ec53d1c13f67650d 100644
--- a/ash/desktop_background/desktop_background_view.h
+++ b/ash/desktop_background/desktop_background_view.h
@@ -5,12 +5,15 @@
 #ifndef ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_
 #define ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_VIEW_H_
 
+#include "ui/events/event.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/views/context_menu_controller.h"
 #include "ui/views/view.h"
 
 namespace ash {
 
+class PreEventDispatchHandler;
+
 class DesktopBackgroundView : public views::View,
                               public views::ContextMenuController {
  public:
@@ -26,6 +29,7 @@ class DesktopBackgroundView : public views::View,
   virtual void ShowContextMenuForView(views::View* source,
                                       const gfx::Point& point,
                                       ui::MenuSourceType source_type) OVERRIDE;
+  scoped_ptr<PreEventDispatchHandler> pre_dispatch_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundView);
 };