Added |lastCommittedURL| and |visibleURL| to Tab's interface.

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 613 matching lines @@
   [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];
+      [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();
+}
+
 - (NSString*)title {
   base::string16 title = self.webState->GetTitle();
   if (title.empty())
     title = l10n_util::GetStringUTF16(IDS_DEFAULT_TAB_TITLE);
   return base::SysUTF16ToNSString(title);
 }
 
 - (NSString*)originalTitle {
   // Do not use self.webState->GetTitle() as it returns the display title,
   // not the original page title.
@@ skipping 1330 matching lines @@
 
 - (TabModel*)parentTabModel {
   return parentTabModel_;
 }
 
 - (FormInputAccessoryViewController*)inputAccessoryViewController {
   return inputAccessoryViewController_.get();
 }
 
 @end