[ios] Removed canGoBack/canGoForward API from CRWSessionController.

ios/web/navigation/crw_session_controller.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/web/navigation/crw_session_controller.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 608 matching lines @@
       self.currentNavigationIndex = [otherSession currentNavigationIndex];
       _previousNavigationIndex = [otherSession previousNavigationIndex];
     } else {
       self.currentNavigationIndex = maxCopyIndex;
     }
   }
   DCHECK_LT((NSUInteger)_currentNavigationIndex, [_entries count]);
   DCHECK(_pendingEntryIndex == -1 || _pendingEntry);
 }
 
-- (BOOL)canGoBack {
-  return [self canGoDelta:-1];
-}
-
-- (BOOL)canGoForward {
-  return [self canGoDelta:1];
-}
-
 - (BOOL)canGoDelta:(int)delta {
   NSInteger index = [self indexOfEntryForDelta:delta];
   return 0 <= index && static_cast<NSUInteger>(index) < _entries.count;
 }
 
 - (void)goDelta:(int)delta {
   if (delta != 0 && [self canGoDelta:delta]) {
     NSInteger newNavigationIndex = [self indexOfEntryForDelta:delta];
     [self goToEntry:_entries[newNavigationIndex]];
   }
@@ skipping 229 matching lines @@
   return [[CRWSessionEntry alloc] initWithNavigationItem:std::move(item)];
 }
 
 - (BOOL)isRedirectTransitionForEntryAtIndex:(NSInteger)index {
   ui::PageTransition transition =
       [_entries[index] navigationItem]->GetTransitionType();
   return (transition & ui::PAGE_TRANSITION_IS_REDIRECT_MASK) ? YES : NO;
 }
 
 @end