[ios] Expose TabModel underlying WebStateList.

ios/chrome/browser/tabs/tab_model.h

 // Copyright 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 IOS_CHROME_BROWSER_TABS_TAB_MODEL_H_
 #define IOS_CHROME_BROWSER_TABS_TAB_MODEL_H_
 
 #import <Foundation/Foundation.h>
 #import <UIKit/UIKit.h>
 
 #include <memory>
 
 #import "ios/web/public/navigation_manager.h"
 #include "ui/base/page_transition_types.h"
 
 class GURL;
 class SessionID;
 @class SessionServiceIOS;
 @class SessionWindowIOS;
 @class Tab;
 @protocol TabModelObserver;
 class TabModelSyncedWindowDelegate;
 class TabUsageRecorder;
+class WebStateList;
 
 namespace ios {
 class ChromeBrowserState;
 }
 
 namespace web {
 struct Referrer;
 class WebState;
 }
 
@@ skipping 72 matching lines @@
 
 // YES if this tab set is off the record.
 @property(nonatomic, readonly, getter=isOffTheRecord) BOOL offTheRecord;
 
 // NO if the model has at least one tab.
 @property(nonatomic, readonly, getter=isEmpty) BOOL empty;
 
 // Determines the number of tabs in the model.
 @property(nonatomic, readonly) NSUInteger count;
 
+// The WebStateList owned by the TabModel.
+@property(nonatomic, readonly) WebStateList* webStateList;
+
 // Initializes tabs from a restored session. |-setCurrentTab| needs to be called
 // in order to display the views associated with the tabs. Waits until the views
 // are ready. |browserState| cannot be nil. |service| cannot be nil; this class
 // creates intermediate SessionWindowIOS objects which must be consumed by a
 // session service before they are deallocated. |window| can be nil to create
 // an empty TabModel. In that case no notification will be sent during object
 // creation.
 - (instancetype)initWithSessionWindow:(SessionWindowIOS*)window
                        sessionService:(SessionServiceIOS*)service
                          browserState:(ios::ChromeBrowserState*)browserState
@@ skipping 143 matching lines @@
 - (void)didCloseTab:(Tab*)closedTab;
 // Called by |tab| to inform the model that a navigation has taken place.
 // TODO(crbug.com/661983): once more of the navigation state has moved into WC,
 // replace this with WebStateObserver.
 - (void)navigationCommittedInTab:(Tab*)tab
                     previousItem:(web::NavigationItem*)previousItem;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_TABS_TAB_MODEL_H_