Rip out dart:io from pkg/http wherever possible.

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;
+import 'package:http_parser/http_parser.dart';
 
 import 'credentials.dart';
 import 'authorization_exception.dart';
 
 /// The amount of time, in seconds, to add as a "grace period" for credential
 /// expiration. This allows credential expiration checks to remain valid for a
 /// reasonable amount of time.
 const _EXPIRATION_GRACE = 10;
 
 /// Handles a response from the authorization server that contains an access
 /// token. This response format is common across several different components of
 /// the OAuth2 flow.
 Credentials handleAccessTokenResponse(
     http.Response response,
     Uri tokenEndpoint,
     DateTime startTime,
     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);
-  }
+  if (contentType != null) contentType = new MediaType.parse(contentType);
 
   // The spec requires a content-type of application/json, but some endpoints
   // (e.g. Dropbox) serve it as text/javascript instead.
   validate(contentType != null &&
-      (contentType.value == "application/json" ||
-       contentType.value == "text/javascript"),
+      (contentType.mimeType == "application/json" ||
+       contentType.mimeType == "text/javascript"),
       'content-type was "$contentType", expected "application/json"');
 
   var parameters;
   try {
     parameters = JSON.decode(response.body);
   } on FormatException catch (e) {
     validate(false, 'invalid JSON');
   }
 
   for (var requiredParameter in ['access_token', 'token_type']) {
@@ skipping 45 matching lines @@
   if (response.statusCode != 400 && response.statusCode != 401) {
     var reason = '';
     if (response.reasonPhrase != null && !response.reasonPhrase.isEmpty) {
       ' ${response.reasonPhrase}';
     }
     throw new FormatException('OAuth request for "$tokenEndpoint" failed '
         'with status ${response.statusCode}$reason.\n\n${response.body}');
   }
 
   var contentType = response.headers['content-type'];
-  if (contentType != null) {
-    contentType = ContentType.parse(contentType);
-  }
-  validate(contentType != null && contentType.value == "application/json",
+  if (contentType != null) contentType = new MediaType.parse(contentType);
+  validate(contentType != null && contentType.mimeType == "application/json",
       'content-type was "$contentType", expected "application/json"');
 
   var parameters;
   try {
     parameters = JSON.decode(response.body);
   } on FormatException catch (e) {
     validate(false, 'invalid JSON');
   }
 
   validate(parameters.containsKey('error'),
@@ skipping 16 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}');
 }