[Navigation Experiment] Add WKBasedNavigationManagerImpl.

ios/web/navigation/navigation_manager_impl.h

 // Copyright 2013 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_NAVIGATION_MANAGER_IMPL_H_
 #define IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_IMPL_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 114 matching lines @@
   virtual int GetIndexForOffset(int offset) const = 0;
 
   // Returns the index of the previous item. Only used by SessionStorageBuilder.
   virtual int GetPreviousItemIndex() const = 0;
 
  protected:
   // The SessionStorageBuilder functions require access to private variables of
   // NavigationManagerImpl.
   friend SessionStorageBuilder;
 
+  // TODO(crbug.com/738020): Remove legacy code and merge
+  // WKBasedNavigationManager into this class after the navigation experiment.
+
   // Identical to GetItemAtIndex() but returns the underlying NavigationItemImpl
   // instead of the public NavigationItem interface. This is used by
   // SessionStorageBuilder to persist session state.
   virtual NavigationItemImpl* GetNavigationItemImplAtIndex(
       size_t index) const = 0;
+
+  // Checks whether or not two URL are an in-page navigation (differing only
+  // in the fragment).
+  static bool AreUrlsFragmentChangeNavigation(const GURL& existing_url,
+                                              const GURL& new_url);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_IMPL_H_