Remove Tab's |-url| property.

ios/chrome/browser/tabs/tab.mm

 // 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.
 
 #import "ios/chrome/browser/tabs/tab.h"
 
 #import <CoreLocation/CoreLocation.h>
 #import <UIKit/UIKit.h>
 
 #include <utility>
@@ skipping 572 matching lines @@
 }
 
 - (void)retrieveSnapshot:(void (^)(UIImage*))callback {
   [_webControllerSnapshotHelper
       retrieveSnapshotForWebController:self.webController
                              sessionID:self.tabId
                           withOverlays:[self snapshotOverlays]
                               callback:callback];
 }
 
-- (const GURL&)url {
-  // See note in header; this method should be removed.
-  web::NavigationItem* item =
-      [self navigationManagerImpl]->GetSessionController().currentItem;
-  return item ? item->GetVirtualURL() : GURL::EmptyGURL();
-}
-
 - (const GURL&)lastCommittedURL {
   web::NavigationItem* item = self.navigationManager->GetLastCommittedItem();
   return item ? item->GetVirtualURL() : GURL::EmptyGURL();
 }
 
 - (const GURL&)visibleURL {
   web::NavigationItem* item = self.navigationManager->GetVisibleItem();
   return item ? item->GetVirtualURL() : GURL::EmptyGURL();
 }
 
@@ skipping 1298 matching lines @@
 
 - (TabModel*)parentTabModel {
   return _parentTabModel;
 }
 
 - (FormInputAccessoryViewController*)inputAccessoryViewController {
   return _inputAccessoryViewController;
 }
 
 @end