Improve resize logic for native

[dgirardi]

This is a partial fix for #191 (does not address the case where GPT is set to allowPushExpansion, which needs a change on the Prebid side).

The iframe resize request is now done when the window has completed loading instead of when the rendering logic completes - which gives time for images, scripts, etc to be done.

Tested on Chrome and FF using the same test page from #190.

[musikele]

noted that postRenderAd is called before the actual resize has been called.

[musikele]

the resize function must contain also the postRenderAd call otherwise postRenderAd is called before the ad has been rendered:

const resize = () => {
    requestHeightResize(bid.adId, (document.body.clientHeight || document.body.offsetHeight), document.body.clientWidth); 
    if (typeof window.postRenderAd === 'function') {
      window.postRenderAd(bid);
      }
    }

[musikele]

and this piece should be removed from here

[dgirardi]

To me this looks correct:

at this point we are done rendering, and the resize function is scheduled to run when the DOM is done loading ( image sources and so on). If we run postRenderAd here it can manipulate the DOM and for example add another image that wold still come in time for resize.

[musikele]

In one of our templates we retrieve the height of the ad, and we do that in postRenderAd. I was thinking that the height should be calculated when we're 100% sure that the resize has happened. So, if document.readyState is not complete, postRenderAd is executed before resize.

[musikele]

Hi there, there are a few comments i've written down, please give a look

EDIT: Sorry I don't understand how I could add a second review request under this PR, and I can't find a way to remove it.

[patmmccann]

fixes #191

[musikele]

LGTM.

I've also tested it with a render function that uses postRenderAd and everything seems to work fine.

I wanted to consider another issue