anchor.diff:    copyDirectory(
         joinDir(Directory.current, ['packages']),
         joinDir(Directory.current, ['app', 'packages']));
  -
  +}
  +
  +void prepareBuild(GrinderContext context) {
  +  context.log('prepare build');
     // Copy files to build directory.
     copyFile(
         joinFile(Directory.current, ['pubspec.yaml']),
  
positive.code: 
  void dart2JSBuild(GrinderContext context) {
    // We remove the symlink and replace it with a copy.
    Process.runSync('rm', ['-rf', 'web/packages']);
    copyDirectory(
        joinDir(Directory.current, ['packages']),
        joinDir(Directory.current, ['web', 'packages']));
  
negative.code: }
  
  Future compile(GrinderContext context) {
    prepareBuild(context);
  
    Directory.current = 'build';
    return Future.wait([asyncPolymerBuild(context,
                                          'web/spark.html',
                                          'polymer-build').then((bool success) {
      Directory.current = 'polymer-build';
      dart2JSBuild(context);
  