Add helper getters for URIs and date/times to json_rpc_2.

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

 // Copyright (c) 2014, 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.barback.web_socket_api;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
@@ skipping 72 matching lines @@
   ///     http://localhost:1234/index.html    -> NOT_SERVED error
   ///
   /// This does *not* currently support the implicit index.html behavior that
   /// pub serve provides for user-friendliness:
   ///
   ///     http://localhost:1234 -> NOT_SERVED error
   ///
   /// This does *not* currently check to ensure the asset actually exists. It
   /// only maps what the corresponding asset *should* be for that URL.
   Map _urlToAssetId(json_rpc.Parameters params) {
-    // TODO(nweiz): Use [params.asUrl] when issue 17700 is fixed.
-    var urlString = params["url"].asString;
-    var url;
-    try {
-      url = Uri.parse(urlString);
-    } on FormatException catch (ex) {
-      throw new json_rpc.RpcException.invalidParams(
-          '"$urlString" is not a valid URL.');
-    }
+    var url = params["url"].asUrl;
 
     // If a line number was given, map it to the output line.
     var line = params["line"].asIntOr(null);
 
     var id = _environment.getAssetIdForUrl(url);
     if (id == null) {
       throw new json_rpc.RpcException(_NOT_SERVED,
           '"${url.host}:${url.port}" is not being served by pub.');
     }
 
@@ skipping 160 matching lines @@
 
     if (!path.isWithin(".", pathString)) {
       throw new json_rpc.RpcException.invalidParams(
           '"$key" cannot reach out of its containing directory. '
           'Got "$pathString".');
     }
 
     return pathString;
   }
 }