Add browser tags to all of our tests.

test/runner/browser/loader_test.dart

 // Copyright (c) 2015, 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.
 
 @TestOn("vm")
+@Tags(const ["chrome"])
 
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:test/src/backend/state.dart';
 import 'package:test/src/backend/test_platform.dart';
 import 'package:test/src/runner/configuration.dart';
 import 'package:test/src/runner/loader.dart';
 import 'package:test/src/util/io.dart';
 import 'package:test/test.dart';
@@ skipping 145 matching lines @@
         .toList();
     expect(suites, hasLength(1));
     var loadSuite = suites.first;
 
     var liveTest = await loadSuite.group.entries.single.load(loadSuite);
     expect(liveTest.onPrint.first, completion(equals("print within test")));
     await liveTest.run();
     expectTestPassed(liveTest);
   });
 }