Refactor app list event handling and prerendering.

ui/app_list/views/apps_grid_view.h

Index: ui/app_list/views/apps_grid_view.h
diff --git a/ui/app_list/views/apps_grid_view.h b/ui/app_list/views/apps_grid_view.h
index 6a94e409e92cd526f744c417da3d9602473445dc..0e470a28bd125a96fb7eb1882d1e8d9b0243c2fa 100644
--- a/ui/app_list/views/apps_grid_view.h
+++ b/ui/app_list/views/apps_grid_view.h
@@ -117,8 +117,8 @@ class APP_LIST_EXPORT AppsGridView : public views::View,
   void SetDragAndDropHostOfCurrentAppList(
       ApplicationDragAndDropHost* drag_and_drop_host);
 
-  // Prerenders the icons on and around |page_index|.
-  void Prerender(int page_index);
+  // Prerenders the icons on and around the currently selected page.
+  void Prerender();
 
   // Return true if the |bounds_animator_| is animating |view|.
   bool IsAnimatingView(views::View* view);
@@ -134,6 +134,7 @@ class APP_LIST_EXPORT AppsGridView : public views::View,
   virtual void Layout() OVERRIDE;
   virtual bool OnKeyPressed(const ui::KeyEvent& event) OVERRIDE;
   virtual bool OnKeyReleased(const ui::KeyEvent& event) OVERRIDE;
+  virtual bool OnMouseWheel(const ui::MouseWheelEvent& event) OVERRIDE;
   virtual void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) OVERRIDE;
   virtual bool GetDropFormats(
@@ -142,6 +143,10 @@ class APP_LIST_EXPORT AppsGridView : public views::View,
   virtual bool CanDrop(const OSExchangeData& data) OVERRIDE;
   virtual int OnDragUpdated(const ui::DropTargetEvent& event) OVERRIDE;
 
+  // Overridden from ui::EventHandler:
+  virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
+  virtual void OnScrollEvent(ui::ScrollEvent* event) OVERRIDE;
+
   // Stops the timer that triggers a page flip during a drag.
   void StopPageFlipTimer();