[Mac] Refactor the logic of tab dragging out of TabView and into a new helper.

chrome/browser/ui/cocoa/tabs/tab_strip_controller.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_CONTROLLER_H_
 #define CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_CONTROLLER_H_
 #pragma once
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/memory/scoped_nsobject.h"
 #include "base/memory/scoped_ptr.h"
 #import "chrome/browser/ui/cocoa/tab_contents/tab_contents_controller.h"
 #import "chrome/browser/ui/cocoa/tabs/tab_controller_target.h"
 #import "chrome/browser/ui/cocoa/url_drop_target.h"
 #include "chrome/browser/ui/tabs/hover_tab_selector.h"
 #import "third_party/GTM/AppKit/GTMWindowSheetController.h"
 
 @class CrTrackingArea;
 @class NewTabButton;
 @class ProfileMenuButton;
 @class TabContentsController;
 @class TabView;
+@class TabStripDragController;
 @class TabStripView;
 
 class Browser;
 class ConstrainedWindowMac;
 class TabStripModelObserverBridge;
 class TabStripModel;
 class TabContents;
 class ToolbarModel;
 
 namespace TabStripControllerInternal {
@@ skipping 39 matching lines @@
   BOOL verticalLayout_;
 
  @private
   scoped_nsobject<TabStripView> tabStripView_;
   NSView* switchView_;  // weak
   scoped_nsobject<NSView> dragBlockingView_;  // avoid bad window server drags
   NewTabButton* newTabButton_;  // weak, obtained from the nib.
   ProfileMenuButton* profileMenuButton_;  // weak, obtained from the nib.
   BOOL hasUpdatedProfileMenuButtonXOffset_;
 
+  // The controller that manages all the interactions of dragging tabs.
+  scoped_nsobject<TabStripDragController> dragController_;
+
   // Tracks the newTabButton_ for rollovers.
   scoped_nsobject<CrTrackingArea> newTabTrackingArea_;
   scoped_ptr<TabStripModelObserverBridge> bridge_;
   Browser* browser_;  // weak
   TabStripModel* tabStripModel_;  // weak
   // Delegate that is informed about tab state changes.
   id<TabStripControllerDelegate> delegate_;  // weak
 
   // YES if the new tab button is currently displaying the hover image (if the
   // mouse is currently over the button).
@@ skipping 177 matching lines @@
 - (void)attachConstrainedWindow:(ConstrainedWindowMac*)window;
 - (void)removeConstrainedWindow:(ConstrainedWindowMac*)window;
 
 @end
 
 // Notification sent when the number of tabs changes. The object will be this
 // controller.
 extern NSString* const kTabStripNumberOfTabsChanged;
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_CONTROLLER_H_