Revert of Replace RenderFullScreen with top layer

Revert r165710 because of unit test failures.

TBR=gavinp

Review URL: https://codereview.chromium.org/130983006

git-svn-id: svn://svn.chromium.org/blink/trunk@165801 bbb929c8-8fbe-4397-9dbb-9b2b20218538