Add browser tags to all of our tests.

test/runner/browser/compact_reporter_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")
 
 import 'package:scheduled_test/descriptor.dart' as d;
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../io.dart';
@@ skipping 16 matching lines @@
     var test = runTest([
       "-p", "content-shell",
       "-p", "vm",
       "-j", "1",
       "test.dart"
     ], reporter: "compact");
 
     test.stdout.expect(containsInOrder(["[VM]", "[Dartium Content Shell]"]));
 
     test.shouldExit(0);
-  });
+  }, tags: 'content-shell');
 }