Don't recalculate style synchronously on hover/active.

At the end of Document::updateHoverActiveState, we did a synchronous update
of style and layout. That caused a :hover + onmouseover changing a class to
trigger two style recalcs.

There were no obvious reasons why the callers of that method expected the
recalc + layout to happen either.

R=abarth@chromium.org,esprehn@chromium.org
BUG=361164

Review URL: https://codereview.chromium.org/229413006

git-svn-id: svn://svn.chromium.org/blink/trunk@171147 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Overlay fullscreen video should remove fixed background layer.

Overlay fullscreen video removes all layers other than the video layer
by re-rooting the tree. Fixed background layer is a special layer
outside the RenderView layer tree. We need to remove it separately.

BUG=356185

Review URL: https://codereview.chromium.org/229613002

git-svn-id: svn://svn.chromium.org/blink/trunk@171148 bbb929c8-8fbe-4397-9dbb-9b2b20218538