Use browsers JSON.parse for parsing JSON (#3)

runtime/lib/json_patch.dart

Index: runtime/lib/json_patch.dart
diff --git a/tests/lib/async/deferred/deferred_api_library.dart b/runtime/lib/json_patch.dart
similarity index 63%
copy from tests/lib/async/deferred/deferred_api_library.dart
copy to runtime/lib/json_patch.dart
index b59077065dc8212ef534fa68b211f0e705126ff7..0b637a15f40b9ed514e80097394caf78d5b88517 100644
--- a/tests/lib/async/deferred/deferred_api_library.dart
+++ b/runtime/lib/json_patch.dart
@@ -2,11 +2,8 @@
 // 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.
 
-// Imported by deferred_api_test.dart.
+// JSON parsing and serialization.
 
-library deferred_api_library;
-
-foo(x) {
-  print('foo($x)');
-  return 42;
+patch parse(String json, [reviver(var key, var value)]) {
+  return _parse(json, reviver);
 }