[whatwg] seamless iframes

[Ojan Vafai]

1.  We should add iframe[seamless] { display:block; }.
http://www.whatwg.org/specs/web-apps/current-work/#embedded-content-2 already
expects iframe:not([seamless]) { border: 2px inset; }. In 90% percent of
uses, seamless iframes will not want a border and will want to fill their
container. This way, seamless iframes behave roughly like sandboxable divs,
which is what web developers want.

2. http://www.whatwg.org/specs/web-apps/current-work/#attr-iframe-seamless "In
visual media, in a CSS-supporting user agent: the user agent should set the
intrinsic width of the iframe to the width that the element would have if
it was a non-replaced block-level element with 'width: auto'."

This doesn't get the behavior you'd want with cases that need
shrink-wrapped behavior. Some cases that need handling:
<iframe seamless style="display:inline">
<iframe seamless style="display:inline-block">
<iframe seamless style="float:left">
<iframe seamless style="position:absolute">

Ojan