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

content/public/browser/navigation_handle.h

Index: content/public/browser/navigation_handle.h
diff --git a/content/public/browser/navigation_handle.h b/content/public/browser/navigation_handle.h
index 3c00e4a10afac5959e7ad7e89b67801980ffcf6d..a2b22e3e570bb8b00793ea2c7b0a5273f9912ec9 100644
--- a/content/public/browser/navigation_handle.h
+++ b/content/public/browser/navigation_handle.h
@@ -151,7 +151,10 @@ class CONTENT_EXPORT NavigationHandle {
   // 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;