code: function downloadCef(version,cb){
  
      var zlib = require('zlib')
        , tar = require('tar')
        , distUrl = 'https://github.com/downloads/appjs/appjs'
        , version = version
        , dirname = 'cef_binary_' + version + '_' + platform + '_' + arch
        , fileName = dirname + '.tar.gz';
  
      var tarballUrl = distUrl + '/' + fileName
        , gunzip     = zlib.createGunzip()
        , extracter  = tar.Extract({ path: depsDir });
  
      var errorHandler = function(err,res){
          if ( err || res.statusCode != 200 ) {
              cb(err || new Error(res.statusCode + ' status code downloading tarball'));
          }
      };
  
      var finish = function() {
        if(platform == 'win32') {
  
          try {
            fs.rmdirSync( path.join(depsDir,'cef') );
          } catch(e) {};
  
          fs.rename(path.join(depsDir, dirname), path.join(depsDir,'cef'),cb);
        } else {
  
          try {
            fs.unlinkSync( path.join(depsDir,'cef') );
          } catch(e) {};
  
          fs.symlink( path.join(depsDir, dirname), path.join(depsDir,'cef') ,cb);
        }
      };
  
      gunzip.on('error', errorHandler)
      extracter.on('error', errorHandler)
      extracter.on('end', finish)
  
      fs.exists(path.join(depsDir, dirname), function(exists) {
        if (!exists) {
          download(tarballUrl,errorHandler)
            .pipe(gunzip)
            .pipe(extracter);
        } else {
          finish();
        }
      });
  }
docs: Downloads CEF binary package according to
  developer's platform and extracts it to
  deps/cef