[ios] Removed canGoBack/canGoForward API from CRWSessionController.

ios/web/navigation/navigation_manager_impl.mm

Index: ios/web/navigation/navigation_manager_impl.mm
diff --git a/ios/web/navigation/navigation_manager_impl.mm b/ios/web/navigation/navigation_manager_impl.mm
index aed46fa3027e0f7b4088362593746ff01dc5f187..d5cba31cb1a5f9c0de9e0a02196dd3c1bd6cb212 100644
--- a/ios/web/navigation/navigation_manager_impl.mm
+++ b/ios/web/navigation/navigation_manager_impl.mm
@@ -287,11 +287,15 @@ bool NavigationManagerImpl::RemoveItemAtIndex(int index) {
 }
 
 bool NavigationManagerImpl::CanGoBack() const {
-  return [session_controller_ canGoBack];
+  return CanGoToOffset(-1);
 }
 
 bool NavigationManagerImpl::CanGoForward() const {
-  return [session_controller_ canGoForward];
+  return CanGoToOffset(1);
+}
+
+bool NavigationManagerImpl::CanGoToOffset(int offset) const {
+  return [session_controller_ canGoDelta:offset];
 }
 
 void NavigationManagerImpl::GoBack() {