Delete pop-pop-win from the repo

samples/pop_pop_win/lib/src/platform.dart

-// Copyright (c) 2014, 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.
-library pop_pop_win.platform;
-
-import 'package:pop_pop_win/platform_target.dart';
-
-PlatformTarget _platformImpl;
-
-void initPlatform(PlatformTarget value) {
-  assert(value != null);
-  assert(!value.initialized);
-  assert(_platformImpl == null);
-  _platformImpl = value;
-  _platformImpl.initialize();
-}
-
-PlatformTarget get targetPlatform {
-  if (_platformImpl == null) {
-    initPlatform(new PlatformTarget());
-  }
-  return _platformImpl;
-}