CDVUIWebView performs javascript synchronous, but command queue expects it to be async

From https://issues.apache.org/jira/browse/CB-10530 regarding app freezing at launch.

...
However I was not sure about why the timer resolves due to long script execution times though. It seems like the intention is that whenever gap://ready is loaded in the iframe, the immediate response from the native side should be to call nativeFetchMessages() which should clear the timeout.

Therefore I dug a little deeper in the native side, and found that the evaluateJavaScript:completionHandler: in CDVCommandQueue expects implementation to to be async (a comment in the code says so), but the CDVUIWebViewEngine method actually is implemented synchronous.
I wrapped the entire method in a dispatch_async call (maybe a very naive solution, it might mess with references?):

dispatch_async(dispatch_get_main_queue(), ^{
  NSString* ret = [(UIWebView*)_engineWebView stringByEvaluatingJavaScriptFromString:javaScriptString];
if (completionHandler)
{ completionHandler(ret, nil); }
});

This also solves the original issue on cordova-ios 4.0.1 as the timeout never resolves, so maybe asyncing this method should also be a part of the proper fix?