[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_
 
+#import <WebKit/WebKit.h>
 #include <stddef.h>
+#include <memory>
 
 #import "ios/web/public/navigation_manager.h"
 
 namespace web {
 
 struct LoadCommittedDetails;
 class WebState;
+class WebViewNavigationProxy;
 
 // Delegate for NavigationManager to hand off parts of the navigation flow.
 class NavigationManagerDelegate {
  public:
   virtual ~NavigationManagerDelegate() {}
 
   // Instructs the delegate to begin navigating to the item with index.
   // TODO(crbug.com/661316): Remove this method once all navigation code is
   // moved to NavigationManagerImpl.
   virtual void GoToIndex(int index) = 0;
 
   // Instructs the delegate to load the URL.
   virtual void LoadURLWithParams(const NavigationManager::WebLoadParams&) = 0;
 
   // Instructs the delegate to reload.
   virtual void Reload() = 0;
 
   // Informs the delegate that committed navigation items have been pruned.
   virtual void OnNavigationItemsPruned(size_t pruned_item_count) = 0;
 
   // 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 the main WKWebView used to display web content.
+  virtual WebViewNavigationProxy* GetWebViewNavigationProxy() const = 0;

[Eugene But (OOO till 7-30), 2017/06/27 22:02:00]

Would it make sense to have
WKBasedNavigationManagerImpl::SetWebViewNavigationProxy instead? We probably not
going to use NavigationManagerDelegate inside WKBasedNavigationManagerImpl
anyway, so at some point the delegate may be removed. 

[danyao, 2017/06/28 22:11:04]

I prefer this over SetWebViewNavigationProxy for a couple of reasons:
1) We still need NavigationManagerDelegate inside the new navigation manager for
notifying observers.
2) CRWWebController might not always have the same WKWebView object. The getter
provides a convenient place to update the point before giving the proxy to
WKBasedNavigationManagerImpl.

[Eugene But (OOO till 7-30), 2017/06/29 01:48:18]

It's just somewhat strange that delegate has Get<Something> method (I know it
already has GetWebState, but that's existing code). Not a big deal though.

If we going to keep the delegate, then maybe we should move all methods from
WebViewNavigationProxy to NavigationManagerDelegate? I'm fine with the code as
it is because it is temporary anyway.

 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_DELEGATE_H_