Observatory: remove unused imports

runtime/observatory/tests/service/issue_27287_test.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.
 // VMOptions=--error_on_bad_type --error_on_bad_override  --verbose_debug
 
-import 'package:observatory/service_io.dart';
 import 'service_test_common.dart';
-import 'dart:async';
 import 'test_helper.dart';
 import 'dart:developer';
 
 const int LINE_A = 19;

[Cutch, 2016/11/15 22:17:12]

here too

[kevmoo, 2016/11/15 23:00:36]

Done.

 const int LINE_B = 20;
 
 var libVariable;
 
 testMain() {
   debugger();
   print("Before");  // LINE_A
   libVariable = 0;  // LINE_B
   print("and after");
 }
 
 var tests = [
   hasStoppedAtBreakpoint,
   stoppedAtLine(LINE_A),
   stepOver,
   // Check that debugger stops at assignment to top-level variable.
   stoppedAtLine(LINE_B),
   resumeIsolate,
 ];
 
 main(args) => runIsolateTests(args, tests, testeeConcurrent: testMain);