Convert json_rpc.Server to take a Stream and StreamSink.

sdk/lib/_internal/pub/lib/src/barback/web_socket_api.dart

Index: sdk/lib/_internal/pub/lib/src/barback/web_socket_api.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/web_socket_api.dart b/sdk/lib/_internal/pub/lib/src/barback/web_socket_api.dart
index 7952dcf9efabbf63cbf15ba62039f8824526e2ea..dc7b3c021fbd20bc41352ab3076f53f871cce4b9 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/web_socket_api.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/web_socket_api.dart
@@ -20,11 +20,11 @@ import 'asset_environment.dart';
 /// This is a [JSON-RPC 2.0](http://www.jsonrpc.org/specification) server. Its
 /// methods are described in the method-level documentation below.
 class WebSocketApi {
-  final CompatibleWebSocket _socket;
   final AssetEnvironment _environment;
-  final _server = new json_rpc.Server();
+  final json_rpc.Server _server;
 
-  WebSocketApi(this._socket, this._environment) {
+  WebSocketApi(CompatibleWebSocket socket, this._environment)
+      : _server = new json_rpc.Server(socket) {
     _server.registerMethod("urlToAssetId", _urlToAssetId);
     _server.registerMethod("pathToUrls", _pathToUrls);
     _server.registerMethod("serveDirectory", _serveDirectory);
@@ -36,13 +36,7 @@ class WebSocketApi {
   /// Returns a future that completes when the socket has closed. It will
   /// complete with an error if the socket had an error, otherwise it will
   /// complete to `null`.
-  Future listen() {
-    return _socket.listen((request) {
-      _server.parseRequest(request).then((response) {
-        if (response != null) _socket.add(response);
-      });
-    }, cancelOnError: true).asFuture();
-  }
+  Future listen() => _server.listen();
 
   /// Given a URL to an asset that is served by pub, returns the ID of the
   /// asset that would be accessed by that URL.