Converted Observatory error-view element

runtime/observatory/tests/observatory_ui/mocks/objects/error.dart

 // Copyright (c) 2016, 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.
 
 part of mocks;
 
 class ErrorRefMock implements M.ErrorRef {
   final String id;
   final M.ErrorKind kind;
   final String message;
-  const ErrorRefMock({this.id, this.kind, this.message});
+
+  const ErrorRefMock({this.id: 'error-ref',
+                      this.kind: M.ErrorKind.internalError,
+                      this.message: 'Error Message'});
 }
 
 class ErrorMock implements M.Error {
   final String id;
   final M.ClassRef clazz;
   final int size;
   final M.ErrorKind kind;
   final String message;
-  const ErrorMock({this.id, this.clazz, this.size, this.kind, this.message});
+
+  const ErrorMock({this.id: 'error-id', this.clazz: const ClassMock(),
+                   this.size: 0, this.kind: M.ErrorKind.internalError,
+                   this.message: 'Error Message'});
 }