Fix all Observatory warnings/errors.

runtime/observatory/test/test_helper.dart

 // Copyright (c) 2013, 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.
 // VMOptions=--compile-all --error_on_bad_type --error_on_bad_override --checked
 
 library test_helper;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
-import 'package:unittest/unittest.dart';
 import 'package:observatory/service_io.dart';
 
 // This invocation should set up the state being tested.
 const String _TESTEE_MODE_FLAG = "--testee-mode";
 
 class _TestLauncher {
   Process process;
   final List<String> args;
 
   _TestLauncher() : args = ['--enable-vm-service:0',
@@ skipping 137 matching lines @@
       var name = Platform.script.pathSegments.last;
       new WebSocketVM(new WebSocketVMTarget(addr)).load()
           .then((VM vm) => Future.forEach(tests, (test) {
             print('Running $name [$testIndex/$totalTests]');
             testIndex++;
             return test(vm);
           })).then((_) => process.requestExit());
     });
   }
 }