Use dartfmt on Observatory code

runtime/observatory/lib/src/models/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 models;
 
 enum ErrorKind {
   /// The isolate has encountered an unhandled Dart exception.
   unhandledException,
+
   /// The isolate has encountered a Dart language error in the program.
   languageError,
+
   /// The isolate has encounted an internal error. These errors should be
   /// reported as bugs.
   internalError,
+
   /// The isolate has been terminated by an external source.
   terminationError
 }
 
 abstract class ErrorRef extends ObjectRef {
   ErrorKind get kind;
   String get message;
 }
 
-abstract class Error extends Object implements ErrorRef {
-
-}
+abstract class Error extends Object implements ErrorRef {}