Fix the tests.

It seems we tickled a core library inconsistency (dart-lang/sdkdart-lang/json_rpc_2#25655):
although on the VM `FormatException.source` is set for JSON parse
errors, it is not set using dart2js.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1659313002 .
diff --git a/pkgs/json_rpc_2/pubspec.yaml b/pkgs/json_rpc_2/pubspec.yaml
index 630b9cc..0d90546 100644
--- a/pkgs/json_rpc_2/pubspec.yaml
+++ b/pkgs/json_rpc_2/pubspec.yaml
@@ -1,5 +1,5 @@
 name: json_rpc_2
-version: 2.0.0
+version: 2.0.1-dev
 author: Dart Team <misc@dartlang.org>
 description: An implementation of the JSON-RPC 2.0 spec.
 homepage: http://github.com/dart-lang/json_rpc_2
diff --git a/pkgs/json_rpc_2/test/peer_test.dart b/pkgs/json_rpc_2/test/peer_test.dart
index 89ab2d6..ad7ad22 100644
--- a/pkgs/json_rpc_2/test/peer_test.dart
+++ b/pkgs/json_rpc_2/test/peer_test.dart
@@ -174,7 +174,8 @@
         "error": {
           'code': error_code.PARSE_ERROR,
           "message": startsWith("Invalid JSON: "),
-          "data": {'request': '{invalid'}
+          // TODO(nweiz): Always expect the source when sdk#25655 is fixed.
+          "data": {'request': anyOf([isNull, '{invalid'])}
         },
         "id": null
       }));
diff --git a/pkgs/json_rpc_2/test/server/server_test.dart b/pkgs/json_rpc_2/test/server/server_test.dart
index 8cc9c5a..ef2e45b 100644
--- a/pkgs/json_rpc_2/test/server/server_test.dart
+++ b/pkgs/json_rpc_2/test/server/server_test.dart
@@ -113,7 +113,8 @@
         'error': {
           'code': error_code.PARSE_ERROR,
           'message': startsWith("Invalid JSON: "),
-          'data': {'request': 'invalid json {'}
+          // TODO(nweiz): Always expect the source when sdk#25655 is fixed.
+          'data': {'request': anyOf([isNull, 'invalid json {'])}
         },
         'id': null
       });