Do not JSON encode the 'result' of a service rpc.

runtime/observatory/tests/service/malformed_test.dart

Index: runtime/observatory/tests/service/malformed_test.dart
diff --git a/runtime/observatory/tests/service/malformed_test.dart b/runtime/observatory/tests/service/malformed_test.dart
index 1d61a46a73ad06cf914aa2da72d551a4b99fb06f..b5f86dd5c4c753a18f978009a3a7800a56829169 100644
--- a/runtime/observatory/tests/service/malformed_test.dart
+++ b/runtime/observatory/tests/service/malformed_test.dart
@@ -8,22 +8,25 @@ import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 var tests = [
+  (Isolate isolate) async {
+    await isolate.invokeRpc('_respondWithMalformedObject', {}).then((result) {
+      expect(false, isTrue, reason:'Unreachable');
+    }).catchError((ServiceException exception) {
+      expect(exception.kind, equals('ResponseFormatException'));
+      expect(exception.message,
+             startsWith("Response is missing the 'type' field"));
+    });
+  },
 
-(Isolate isolate) =>
-  isolate.invokeRpc('_respondWithMalformedJson', { }).then((result) {
-    // Should not execute.
-    expect(true, false);
-  }).catchError((ServiceException exception) {
-    expect(exception.kind, equals('JSONDecodeException'));
-  }),
-
-(Isolate isolate) =>
-  isolate.invokeRpc('_respondWithMalformedObject', { }).then((result) {
-    // Should not execute.
-    expect(true, false);
-  }).catchError((ServiceException exception) {
-    expect(exception.kind, equals('ResponseFormatException'));
-  }),
+  // Do this test last... it kills the vm connection.
+  (Isolate isolate) async {
+    await isolate.invokeRpc('_respondWithMalformedJson', {}).then((result) {
+      expect(false, isTrue, reason:'Unreachable');
+    }).catchError((ServiceException exception) {
+      expect(exception.kind, equals('ConnectionClosed'));
+      expect(exception.message, startsWith('Error decoding JSON message'));
+    });
+  },
 ];
 
 main(args) => runIsolateTests(args, tests);