Create bindPromiseFn which converts a non native Promise to Native Promise

[mhevery]

Similar to bind() have a method which would allow us to easily capture zone on methods which instead of taking callbacks return Promise

function bindPromiseFn(delegate) {
  return function() {
    var delagtePromise = delegate.apply(this, arguments);
    if (deletaePromise instanceof Promise) {
      return delegatePromise;
    } else {
      return new Promise(function(resolve, reject) { 
        delegatePromise.then(resolve, reject); 
      });
    }
 };
}

See the workaround I had to do to fix an issue: https://github.com/rkirov/youtube-app/pull/1/files