Never use the XML as parsed by the XHR instance. Use raw text instead…

… and let the ajax conversion logic do the trick. -20 min/gzipped. Fixes #13276. Unit test added.

src/ajax/xhr.js

@@ -105,8 +105,7 @@ if ( xhrSupported ) {
 						var status,
 							statusText,
 							responseHeaders,
-							responses,
-							xml;
+							responses;
 
 						// Firefox throws exceptions when accessing properties
 						// of an xhr when a network error occurred
@@ -136,14 +135,8 @@ if ( xhrSupported ) {
 								} else {
 									responses = {};
 									status = xhr.status;
-									xml = xhr.responseXML;
 									responseHeaders = xhr.getAllResponseHeaders();
 
-									// Construct response list
-									if ( xml && xml.documentElement /* #4958 */ ) {
-										responses.xml = xml;
-									}
-
 									// When requesting binary data, IE6-9 will throw an exception
 									// on any attempt to access responseText (#11426)
 									if ( typeof xhr.responseText === "string" ) {

test/unit/ajax.js

@@ -1483,6 +1483,22 @@ module( "ajax", {
 
 	});
 
+	ajaxTest( "#13276 - jQuery.ajax() - compatibility between XML documents from ajax requests and parsed string", 1, {
+		url: "data/dashboard.xml",
+		dataType: "xml",
+		success: function( ajaxXML ) {
+			var parsedXML = jQuery( jQuery.parseXML("<tab title=\"Added\">blibli</tab>") ).find("tab");
+			ajaxXML = jQuery( ajaxXML );
+			try {
+				ajaxXML.find("infowindowtab").append( parsedXML );
+			} catch( e ) {
+				strictEqual( e, undefined, "error" );
+				return;
+			}
+			strictEqual( ajaxXML.find("tab").length, 3, "Parsed node was added properly" );
+		}
+	});
+
 //----------- jQuery.ajaxPrefilter()
 
 	ajaxTest( "jQuery.ajaxPrefilter() - abort", 1, {