Stop JSON-encoding cross-frame messages.

lib/src/runner/browser/static/host.dart

 // Copyright (c) 2015, 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.
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:html';
 import 'dart:js' as js;
 
 import 'package:stack_trace/stack_trace.dart';
 import 'package:stream_channel/stream_channel.dart';
 
 /// The iframes created for each loaded test suite, indexed by the suite id.
 final _iframes = new Map<int, IFrameElement>();
 
-// TODO(nweiz): test this once we can run browser tests.
 /// Code that runs in the browser and loads test suites at the server's behest.
 ///
 /// One instance of this runs for each browser. When the server tells it to load
 /// a test, it starts an iframe pointing at that test's code; from then on, it
 /// just relays messages between the two.
 ///
 /// The browser uses two layers of [MultiChannel]s when communicating with the
 /// server:
 ///
 ///                                       server
@@ skipping 130 matching lines @@
     if (message.data["ready"] == true) {
       readyCompleter.complete();
     } else {
       controller.local.sink.add(message.data["data"]);
     }
   });
 
   controller.local.stream.listen((message) async {
     await readyCompleter.future;
 
-    // JSON-encode the message to work around sdk#25636, which caused the
-    // structured clone algorithm to be broken with Window.postMessage in
-    // 1.14.{0,1,2}. Once we no longer care about these Dartiums, stop encoding.
-    iframe.contentWindow.postMessage(
-        JSON.encode(message), window.location.origin);
+    iframe.contentWindow.postMessage(message, window.location.origin);
   });
 
   return controller.foreign;
 }