Fixes possible crash in tab dragging

chrome/browser/ui/views/tabs/tab_drag_controller.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 CHROME_BROWSER_UI_VIEWS_TABS_TAB_DRAG_CONTROLLER_H_
 #define CHROME_BROWSER_UI_VIEWS_TABS_TAB_DRAG_CONTROLLER_H_
 
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 393 matching lines @@
   void RevertDrag();
 
   // Reverts the tab at |drag_index| in |drag_data_|.
   void RevertDragAt(size_t drag_index);
 
   // Selects the dragged tabs in |model|. Does nothing if there are no longer
   // any dragged contents (as happens when a WebContents is deleted out from
   // under us).
   void ResetSelection(TabStripModel* model);
 
+  // Restores |initial_selection_model_| to the |source_tabstrip_|.
+  void RestoreInitialSelection();
+
   // Finishes a succesful drag operation.
   void CompleteDrag();
 
   // Maximizes the attached window.
   void MaximizeAttachedWindow();
 
   // Resets the delegates of the WebContents.
   void ResetDelegates();
 
   // Create the DraggedTabView.
@@ skipping 234 matching lines @@
   // See comment around use for more details.
   int attach_x_;
   int attach_index_;
 
   base::WeakPtrFactory<TabDragController> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TabDragController);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_TABS_TAB_DRAG_CONTROLLER_H_