Added text/javascript as a possible content-type response to the _validate method

pkg/oauth2/lib/src/handle_access_token_response.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library handle_access_token_response;
 
 import 'dart:io';
 import 'dart:convert';
 
 import 'package:http/http.dart' as http;
@@ skipping 16 matching lines @@
     List<String> scopes) {
   if (response.statusCode != 200) _handleErrorResponse(response, tokenEndpoint);
 
   void validate(bool condition, String message) =>
     _validate(response, tokenEndpoint, condition, message);
 
   var contentType = response.headers['content-type'];
   if (contentType != null) {
     contentType = ContentType.parse(contentType);
   }
-  validate(contentType != null && contentType.value == "application/json",
-      'content-type was "$contentType", expected "application/json"');
+  validate(contentType != null && (contentType.value == "application/json" || contentType.value == "text/javascript"),
+      'content-type was "$contentType", expected "application/json" or "text/javascript"');
 
   var parameters;
   try {
     parameters = JSON.decode(response.body);
   } on FormatException catch (e) {
     validate(false, 'invalid JSON');
   }
 
   for (var requiredParameter in ['access_token', 'token_type']) {
     validate(parameters.containsKey(requiredParameter),
@@ skipping 84 matching lines @@
 
 void _validate(
     http.Response response,
     Uri tokenEndpoint,
     bool condition,
     String message) {
   if (condition) return;
   throw new FormatException('Invalid OAuth response for "$tokenEndpoint": '
       '$message.\n\n${response.body}');
 }