Update the CHECK in 'NavigationHandleImpl::GetRenderFrameHost()'

content/public/browser/navigation_handle.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 CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_
 #define CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_
 
 #include <memory>
 
 #include "content/common/content_export.h"
@@ skipping 107 matching lines @@
   // handlers.
   virtual bool IsExternalProtocol() = 0;
 
   // Navigation control flow --------------------------------------------------
 
   // The net error code if an error happened prior to commit. Otherwise it will
   // be net::OK.
   virtual net::Error GetNetErrorCode() = 0;
 
   // Returns the RenderFrameHost this navigation is taking place in. This can
-  // only be accessed after the navigation is ready to commit.
+  // only be accessed after a response has been delivered for processing.
+  //
+  // If PlzNavigate is active, the RenderFrameHost returned will be the final
+  // host for the navigation. If PlzNavigate is inactive, the navigation may
+  // transfer to a new host up until the point that DidFinishNavigation is
+  // called.
   virtual RenderFrameHost* GetRenderFrameHost() = 0;
 
   // Whether the navigation happened in the same page. This is only known
   // after the navigation has committed. It is an error to call this method
   // before the navigation has committed.
   virtual bool IsSamePage() = 0;
 
   // Whether the navigation has encountered a server redirect or not.
   virtual bool WasServerRedirect() = 0;
 
@@ skipping 50 matching lines @@
 
   // The NavigationData that the embedder returned from
   // ResourceDispatcherHostDelegate::GetNavigationData during commit. This will
   // be a clone of the NavigationData.
   virtual NavigationData* GetNavigationData() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_NAVIGATION_HANDLE_H_