<img> setting src = "" should maybe be sync

[zcorpan]

https://html.spec.whatwg.org/#updating-the-image-data

If the element does not use srcset or picture, and it has a src attribute specified and its value is not the empty string, let selected source be the value of the element's src attribute, and selected pixel density be 1.0. Otherwise, let selected source be null and selected pixel density be undefined.

From web-platform-tests/wpt#5060

See http://software.hixie.ch/utilities/js/live-dom-viewer/saved/4936

It seems that in Chromium and Gecko this case is sync (doesn't await a stable state).

With picture: http://software.hixie.ch/utilities/js/live-dom-viewer/saved/4937

Chromium: still sync. Gecko awaits a stable state. Per spec updates shouldn't be sync if srcset or picture are used.

WebKit seems a bit weird for the case of setting src to empty string or removing the src attribute doesn't change .width or the rendered dimensions but it doesn't render the old image.

[zcorpan]

Result in Edge 13 for 4936:

log: 0

[EdgarChen]

See http://software.hixie.ch/utilities/js/live-dom-viewer/saved/4936
It seems that in Chromium and Gecko this case is sync (doesn't await a stable state).

Gecko now always sync loads image for non-responsive case (without picture and srcset), but we intent to change behaviour to follow the current spec, so http://software.hixie.ch/utilities/js/live-dom-viewer/saved/4936 will become async (await a stable state) after https://bugzilla.mozilla.org/show_bug.cgi?id=1076583.

[jdm]

It sounds like we should not necessarily blindly follow the current specification, though.

[zcorpan]

Yeah this a case I probably did not carefully consider before. Though given WebKit's behavior it may not be critical for Web compat either way. But it seems slightly safer to align with majority behavior (in the non-responsive case).

[EdgarChen]

I see, I will also handle this case in https://bugzilla.mozilla.org/show_bug.cgi?id=1076583. Thank you, @zcorpan and @jdm.

[EdgarChen]

Per #4884 (comment), it looks like browsers have different behavior not only in non-responsive case, but also responsive case. :(