Add IsErrorPage comment noting that HTTP error pages are not included.

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 133 matching lines @@
 
   // Whether the navigation has encountered a server redirect or not.
   virtual bool WasServerRedirect() = 0;
 
   // Whether the navigation has committed. This returns true for either
   // successful commits or error pages that replace the previous page
   // (distinguished by |IsErrorPage|), and false for errors that leave the user
   // on the previous page.
   virtual bool HasCommitted() = 0;
 
-  // Whether the navigation resulted in an error page.
+  // Whether the navigation resulted in an error page. This includes
+  // browser-generated error pages, such as the 'There is no Internet
+  // connection' page, but not HTTP error pages, such as those with 4xx or 5xx
+  // response codes.
   // Note that if an error page reloads, this will return true even though
   // GetNetErrorCode will be net::OK.
   virtual bool IsErrorPage() = 0;
 
   // Returns the response headers for the request or nullptr if there are none.
   // This should only be accessed after a redirect was encountered or after the
   // navigation is ready to commit. The headers returned should not be modified,
   // as modifications will not be reflected in the network stack.
   virtual const net::HttpResponseHeaders* GetResponseHeaders() = 0;
 
@@ skipping 52 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_