Added NavigationManager::GetIndexOfItem().

ios/web/navigation/crw_session_controller.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_WEB_NAVIGATION_CRW_SESSION_CONTROLLER_H_
 #define IOS_WEB_NAVIGATION_CRW_SESSION_CONTROLLER_H_
 
 #import <Foundation/Foundation.h>
 #include <vector>
 
@@ skipping 129 matching lines @@
 // Removes the item at |index| after discarding any noncomitted entries.
 // |index| must not be the index of the last committed item, or a noncomitted
 // item.
 - (void)removeItemAtIndex:(NSInteger)index;
 
 // Determines whether a navigation between |firstEntry| and |secondEntry| is a
 // same-document navigation.  Entries can be passed in any order.
 - (BOOL)isSameDocumentNavigationBetweenItem:(web::NavigationItem*)firstItem
                                     andItem:(web::NavigationItem*)secondItem;
 
-// Returns the index of |item| in |items|.
-- (NSInteger)indexOfItem:(const web::NavigationItem*)item;
+// Returns the index of |item| in |items|, or -1 if it is not present.
+- (int)indexOfItem:(const web::NavigationItem*)item;
 
 // Returns the item at |index| in |items|.
 - (web::NavigationItemImpl*)itemAtIndex:(NSInteger)index;
 
 @end
 
 #endif  // IOS_WEB_NAVIGATION_CRW_SESSION_CONTROLLER_H_