Store NavigationIntext in CRWWKNavigationStates.

ios/web/web_state/navigation_context_impl.h

Index: ios/web/web_state/navigation_context_impl.h
diff --git a/ios/web/web_state/navigation_context_impl.h b/ios/web/web_state/navigation_context_impl.h
index 81ab2d5c73088cf7655e6f0ce211af548332aaa1..5756cedf4a711abf6da402cadb8935a7261eae6d 100644
--- a/ios/web/web_state/navigation_context_impl.h
+++ b/ios/web/web_state/navigation_context_impl.h
@@ -18,28 +18,34 @@ namespace web {
 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(
@@ -48,7 +54,6 @@ class NavigationContextImpl : public NavigationContext {
       bool is_same_page,
       bool is_error_page,
       const scoped_refptr<net::HttpResponseHeaders>& response_headers);
-  ~NavigationContextImpl() override;
 
   WebState* web_state_ = nullptr;
   GURL url_;