Created attachment 181603 [details]
See the test case. The current logic came from http://trac.webkit.org/changeset/13723, which itself copy-pasted from RenderReplaced. I tested IE9, FF17 and Opera12. WebKit is the only browser that changes the width due to a percentage height being set.
Since then, this code has been copy-pasted into a few other classes as well. :) I'll post a patch tomorrow.
Created attachment 181711 [details]
Comment on attachment 181711 [details]
View in context: https://bugs.webkit.org/attachment.cgi?id=181711&action=review
> + This makes our behavior match Firefox 17, IE 9 and Opera 12.
I would include the text, "The current logic came from http://trac.webkit.org/changeset/13723, which itself copy-pasted from RenderReplaced."
Committed r139089: <http://trac.webkit.org/changeset/139089>