Reland "Implement FullScreen using top layer."
This reverts commit 2460a95281959d1b4dd941fed10998adf8dcb63c.
Notable changes on top of previous attempt:
full-screen-iframe-ua-style.html is changed to use overflow property
instead, as position is no longer changed on ancestors.
:root:-webkit-full-screen-ancestor { overflow: hidden !important; } is
retained, as the previous attempt regressed on Vimeo (crbug.com/543946)
and it's not clear yet how to handle this in the spec:
https://github.com/whatwg/fullscreen/issues/19
Make ::backdrop work for replaced content (video, iframe, etc.) by
changing StyleResolver::createPseudoElementIfNeeded to allow creating
the ::backdrop pseudo-element even if the parent doesn't support
children. With this change, full-screen-stacking-context.html was
simplified and full-screen-video-has-backdrop.html was
simplified+renamed.
The will-change override is dropped, as full-screen-will-change.html
passes without it.
BUG=240576, 543946
Review-Url: https://codereview.chromium.org/2107233002
Cr-Commit-Position: refs/heads/master@{#405478}
53 files changed
