Fix some observatory analysis issues.

runtime/observatory/tests/service/auth_token1_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
 
 import 'dart:async';
 import 'dart:developer';
 import 'dart:io' as io;
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 Future<Null> testeeBefore() async {
   print('testee before');
   print(await Service.getInfo());
   // Start the web server.
   ServiceProtocolInfo info = await Service.controlWebServer(enable: true);
   expect(info.serverUri, isNotNull);
   // Ensure that we have no auth token in the path segments.
   expect(info.serverUri.pathSegments.length, equals(0));
 
   // Try connecting to the server without the auth token, it should succeed.
   var port = info.serverUri.port;
   var url = Uri.parse('http://localhost:$port');
   var httpClient = new io.HttpClient();
   try {
-    var request = await httpClient.getUrl(url);
+    await httpClient.getUrl(url);
     expect(true, true);
   } catch (e) {
     expect(true, false);
   }
 }
 
 var tests = [
   (Isolate isolate) async {
     await isolate.reload();
     // Just getting here means that the testee enabled the service protocol
     // web server.
     expect(true, true);
   }
 ];
 
 main(args) => runIsolateTests(args, tests,
     testeeBefore: testeeBefore,
     // the testee is responsible for starting the
     // web server.
     testeeControlsServer: true,
     useAuthToken: false);