Update hover state after entering and leaving fullscreen.

The update is scheduled after the render tree is updated and the element
entering / leaving fullscreen has completed what it needs to do.

R=philipj@opera.com
BUG=374716, 376728
Tests= fullscreen/ LayoutTests on Linux

Review URL: https://codereview.chromium.org/552903004

git-svn-id: svn://svn.chromium.org/blink/trunk@182373 bbb929c8-8fbe-4397-9dbb-9b2b20218538