Remove NavigationManager::GetPreviousItem().

ios/web/navigation/crw_session_controller.h

Index: ios/web/navigation/crw_session_controller.h
diff --git a/ios/web/navigation/crw_session_controller.h b/ios/web/navigation/crw_session_controller.h
index c54ec7a62d7497f51c7bab8a359e83dc5422ac65..1554fd638a726182cb83818b03a09b4f1c32dd0c 100644
--- a/ios/web/navigation/crw_session_controller.h
+++ b/ios/web/navigation/crw_session_controller.h
@@ -44,6 +44,8 @@ struct Referrer;
 
 // The list of CRWSessionEntries in |_entries|'s NavigationItemImpls.
 @property(nonatomic, readonly) web::NavigationItemList items;
+// The number of elements in |self.items|.
+@property(nonatomic, readonly) NSUInteger itemCount;
 // The current NavigationItem.  During a pending navigation, returns the
 // NavigationItem for that navigation.  If a transient NavigationItem exists,
 // this NavigationItem will be returned.
@@ -152,6 +154,9 @@ struct Referrer;
 // Returns the index of |item| in |items|.
 - (NSInteger)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_