Add utility methods for sending non-form data in pkg/http.

sdk/lib/_internal/pub/lib/src/command/uploader.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 pub.command.uploader;
 
 import 'dart:async';
 
 import 'package:path/path.dart' as path;
 
@@ skipping 51 matching lines @@
       if (package != null) return package;
       return new Entrypoint(path.current, cache).root.name;
     }).then((package) {
       var uploader = rest[0];
       return oauth2.withClient(cache, (client) {
         if (command == 'add') {
           var url = server.resolve("/api/packages/"
               "${Uri.encodeComponent(package)}/uploaders");
           return client.post(url,
               headers: PUB_API_HEADERS,
-              fields: {"email": uploader});
+              body: {"email": uploader});
         } else { // command == 'remove'
           var url = server.resolve("/api/packages/"
               "${Uri.encodeComponent(package)}/uploaders/"
               "${Uri.encodeComponent(uploader)}");
           return client.delete(url, headers: PUB_API_HEADERS);
         }
       });
     }).then(handleJsonSuccess)
       .catchError((error) => handleJsonError(error.response),
                   test: (e) => e is PubHttpException);
   }
 }