Add isolate tag-profile and better handling of errors

runtime/vm/service/message.dart

Index: runtime/vm/service/message.dart
diff --git a/runtime/vm/service/message.dart b/runtime/vm/service/message.dart
index d6925a77603cd43e096d45d6edc3b794bbff2a9b..908b56fb444fd41dc477b9442fecf9801a11374d 100644
--- a/runtime/vm/service/message.dart
+++ b/runtime/vm/service/message.dart
@@ -90,8 +90,10 @@ class Message {
 
   void setErrorResponse(String error) {
     _completer.complete(JSON.encode({
-        'type': 'Error',
-        'msg': error,
+        'type': 'ServiceError',
+        'id': '',
+        'kind': 'RequestError',
+        'message': error,
         'path': path,
         'options': options
     }));