Fixes #8146. Custom fields in xhrFields are now set after the XMLHttp…

…Request object has been opened.

src/ajax/xhr.js

@@ -85,13 +85,6 @@ if ( jQuery.support.ajax ) {
 						handle,
 						i;
 
-					// Apply custom fields if provided
-					if ( s.xhrFields ) {
-						for ( i in s.xhrFields ) {
-							xhr[ i ] = s.xhrFields[ i ];
-						}
-					}
-
 					// Open the socket
 					// Passing null username, generates a login popup on Opera (#2865)
 					if ( s.username ) {
@@ -100,6 +93,13 @@ if ( jQuery.support.ajax ) {
 						xhr.open( s.type, s.url, s.async );
 					}
 
+					// Apply custom fields if provided
+					if ( s.xhrFields ) {
+						for ( i in s.xhrFields ) {
+							xhr[ i ] = s.xhrFields[ i ];
+						}
+					}
+
 					// Requested-With header
 					// Not set for crossDomain requests with no content
 					// (see why at http://trac.dojotoolkit.org/ticket/9486)