Make dragging outside the app list scroll back to its original position.

ui/app_list/views/apps_grid_view.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_
 #define UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/timer/timer.h"
@@ skipping 204 matching lines @@
 
   // Invoked when |page_flip_timer_| fires.
   void OnPageFlipTimer();
 
   // Updates |model_| to move item represented by |item_view| to |target| slot.
   void MoveItemInModel(views::View* item_view, const Index& target);
 
   // Cancels any context menus showing for app items on the current page.
   void CancelContextMenusOnCurrentPage();
 
+  // Returnes true if |point| lies within the bounds of this grid view plus a
+  // buffer area surrounding it.
+  bool IsPointWithinDragBuffer(const gfx::Point& point) const;
+
   // Overridden from views::ButtonListener:
   virtual void ButtonPressed(views::Button* sender,
                              const ui::Event& event) OVERRIDE;
 
   // Overridden from ListModelObserver:
   virtual void ListItemsAdded(size_t start, size_t count) OVERRIDE;
   virtual void ListItemsRemoved(size_t start, size_t count) OVERRIDE;
   virtual void ListItemMoved(size_t index, size_t target_index) OVERRIDE;
   virtual void ListItemsChanged(size_t start, size_t count) OVERRIDE;
 
@@ skipping 31 matching lines @@
 
   // The point where the drag started in AppListItemView coordinates.
   gfx::Point drag_view_offset_;
 
   // The point where the drag started in GridView coordinates.
   gfx::Point drag_start_grid_view_;
 
   // The location of |drag_view_| when the drag started.
   gfx::Point drag_view_start_;
 
+  // Page the drag started on.
+  int drag_start_page_;
+
 #if defined(OS_WIN) && !defined(USE_AURA)
   // Created when a drag is started (ie: drag exceeds the drag threshold), but
   // not Run() until supplied with a shortcut path.
   scoped_refptr<SynchronousDrag> synchronous_drag_;
 #endif
 
   Pointer drag_pointer_;
   Index drop_target_;
 
   // An application target drag and drop host which accepts dnd operations.
@@ skipping 17 matching lines @@
   int page_flip_delay_in_ms_;
 
   views::BoundsAnimator bounds_animator_;
 
   DISALLOW_COPY_AND_ASSIGN(AppsGridView);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_APPS_GRID_VIEW_H_