[ios] Removed canGoBack/canGoForward API from CRWSessionController.

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 99 matching lines @@
 - (void)insertStateFromSessionController:(CRWSessionController*)otherController;
 
 // Copies history state from the given CRWSessionController and adds it to this
 // controller. If |replaceState|, replaces the state of this controller with
 // the state of |otherSession|, instead of appending.
 // DEPRECATED, use insertStateFromSessionController: instead.
 // TODO(crbug.com/664344): Remove this method.
 - (void)copyStateFromAndPrune:(CRWSessionController*)otherSession
                  replaceState:(BOOL)replaceState;
 
-// Returns YES if there are entries to go back or forward to, given the
-// current entry.
-- (BOOL)canGoBack;
-- (BOOL)canGoForward;
+// Returns YES if there are entries to go with given delta.
 - (BOOL)canGoDelta:(int)delta;
-// Calls goBack or goForward the appropriate number of times to adjust
-// currentNavigationIndex_ by delta.
+// Navigates to the entry with the given |delta|.
 - (void)goDelta:(int)delta;
 // Sets |currentNavigationIndex_| to the index of |entry| if |entries_| contains
 // |entry|.
 - (void)goToEntry:(CRWSessionEntry*)entry;
 
 // Removes the entry at |index| after discarding any noncomitted entries.
 // |index| must not be the index of the last committed entry, or a noncomitted
 // entry.
 - (void)removeEntryAtIndex:(NSInteger)index;
 
@@ skipping 22 matching lines @@
 - (void)useDesktopUserAgentForNextPendingEntry;
 
 // Returns the navigation index that differs from the current entry by the
 // specified |delta|, skipping redirect navigation items. The index returned is
 // not guaranteed to be valid.
 - (NSInteger)indexOfEntryForDelta:(int)delta;
 
 @end
 
 #endif  // IOS_WEB_NAVIGATION_CRW_SESSION_CONTROLLER_H_