Fix static analysis warnings in Observatory

runtime/observatory/tests/ui/inspector.dart

 // Copyright (c) 2014, 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.
 
 // See inspector.txt for expected behavior.
 
 library manual_inspector_test;
 
-import 'dart:async';
 import 'dart:isolate';
 import 'dart:mirrors';
 import 'dart:developer';
 import 'dart:typed_data';
 
 part 'inspector_part.dart';
 
 var libraryField;
 var node;
 var uninitialized = new Object();
@@ skipping 222 matching lines @@
   typed = new Typed();
   node = new Node();
   node.main();
 }
 
 class C {
   static doPrint() {
     print("Original");
   }
 }