Store NavigationIntext in CRWWKNavigationStates.

ios/web/web_state/navigation_context_impl.h

 // Copyright 2017 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_WEB_STATE_NAVIGATION_CONTEXT_IMPL_H_
 #define IOS_WEB_WEB_STATE_NAVIGATION_CONTEXT_IMPL_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "ios/web/public/web_state/navigation_context.h"
 #include "url/gurl.h"
 
 namespace web {
 
 // Tracks information related to a single navigation.
 class NavigationContextImpl : public NavigationContext {
  public:
   // Creates navigation context for sucessful navigation to a different page.
-  static std::unique_ptr<NavigationContext> CreateNavigationContext(
+  static std::unique_ptr<NavigationContextImpl> CreateNavigationContext(
       WebState* web_state,
       const GURL& url,
       const scoped_refptr<net::HttpResponseHeaders>& response_headers);
 
   // Creates navigation context for sucessful same page navigation.
-  static std::unique_ptr<NavigationContext> CreateSameDocumentNavigationContext(
-      WebState* web_state,
-      const GURL& url);
+  static std::unique_ptr<NavigationContextImpl>
+  CreateSameDocumentNavigationContext(WebState* web_state, const GURL& url);
 
   // Creates navigation context for the error page navigation.
-  static std::unique_ptr<NavigationContext> CreateErrorPageNavigationContext(
+  static std::unique_ptr<NavigationContextImpl>
+  CreateErrorPageNavigationContext(
       WebState* web_state,
       const GURL& url,
       const scoped_refptr<net::HttpResponseHeaders>& response_headers);
 
+#ifndef NDEBUG
+  // Returns human readable description of this object.
+  NSString* GetDescription() const;
+#endif  // NDEBUG
+
   // NavigationContext overrides:
   WebState* GetWebState() override;
   const GURL& GetUrl() const override;
   bool IsSameDocument() const override;
   bool IsErrorPage() const override;
   net::HttpResponseHeaders* GetResponseHeaders() const override;
+  ~NavigationContextImpl() override;
 
  private:
   NavigationContextImpl(
       WebState* web_state,
       const GURL& url,
       bool is_same_page,
       bool is_error_page,
       const scoped_refptr<net::HttpResponseHeaders>& response_headers);
-  ~NavigationContextImpl() override;
 
   WebState* web_state_ = nullptr;
   GURL url_;
   bool is_same_document_ = false;
   bool is_error_page_ = false;
   scoped_refptr<net::HttpResponseHeaders> response_headers_;
 
   DISALLOW_COPY_AND_ASSIGN(NavigationContextImpl);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_WEB_STATE_NAVIGATION_CONTEXT_IMPL_H_