[Mac] Fix tabstrip background opacity problem when dragging tabs.

chrome/browser/ui/cocoa/tabs/tab_strip_view.h

 // Copyright (c) 2011 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_COCOA_TABS_TAB_STRIP_VIEW_H_
 #define CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_VIEW_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_nsobject.h"
@@ skipping 14 matching lines @@
 
   // Handles being a drag-and-drop target.
   base::scoped_nsobject<URLDropTargetHandler> dropHandler_;
 
   base::scoped_nsobject<NewTabButton> newTabButton_;
 
   // Whether the drop-indicator arrow is shown, and if it is, the coordinate of
   // its tip.
   BOOL dropArrowShown_;
   NSPoint dropArrowPosition_;
+  BOOL inATabDraggingOverlayWindow_;
 }
 
 @property(assign, nonatomic) BOOL dropArrowShown;
 @property(assign, nonatomic) NSPoint dropArrowPosition;
+@property(assign, nonatomic) BOOL inATabDraggingOverlayWindow;
 
 // Name starts with "get" because methods staring with "new" return retained
 // objects according to Cocoa's create rule.
 - (NewTabButton*)getNewTabButton;
 
 @end
 
 // Interface for the controller to set and clear the weak reference to itself.
 @interface TabStripView (TabStripControllerInterface)
 - (void)setController:(TabStripController*)controller;
 @end
 
 // Protected methods subclasses can override to alter behavior. Clients should
 // not call these directly.
 @interface TabStripView (Protected)
 - (void)drawBottomBorder:(NSRect)bounds;
 - (BOOL)doubleClickMinimizesWindow;
 @end
 
 @interface TabStripView (TestingAPI)
 - (void)setNewTabButton:(NewTabButton*)button;
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_VIEW_H_