[Navigation Experiment] Add WKBasedNavigationManagerImpl.

ios/web/navigation/navigation_manager_delegate.h

 // Copyright 2015 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_DELEGATE_H_
 #define IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_DELEGATE_H_
 
 #include <stddef.h>
 
 #import "ios/web/public/navigation_manager.h"
 
+@protocol CRWWebViewNavigationProxy;
+
 namespace web {
 
 struct LoadCommittedDetails;
 class WebState;
 
 // Delegate for NavigationManager to hand off parts of the navigation flow.
 class NavigationManagerDelegate {
  public:
   virtual ~NavigationManagerDelegate() {}
 
@@ skipping 13 matching lines @@
 
   // Informs the delegate that a navigation item has been changed.
   virtual void OnNavigationItemChanged() = 0;
 
   // Informs the delegate that a navigation item has been commited.
   virtual void OnNavigationItemCommitted(
       const LoadCommittedDetails& load_details) = 0;
 
   // Returns the WebState associated with this delegate.
   virtual WebState* GetWebState() = 0;
+
+  // Returns a CRWWebViewNavigationProxy protocol that can be used to access
+  // navigation related functions on the main WKWebView.
+  virtual id<CRWWebViewNavigationProxy> GetWebViewNavigationProxy() const = 0;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_DELEGATE_H_