Revert of Retry "Replace RenderFullScreen with top layer" (https://codereview.chromium.org/142653003/)

Reason for revert:
Flaky crashes on full-screen-element-stack.html
http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux/builds/26189

This test also crashed after the last attempt, but it looked like it was not due to this patch since it kept crashing well after that patch was reverted. It looks real now though.

Original issue's description:
> Retry "Replace RenderFullScreen with top layer"
> 
> This patch makes the Fullscreen API use the top layer, as per the latest
> Fullscreen spec. This retry fixes some tests/expectations.
> 
> Previously landed as r165904 and r165710
> Codereviews:
> https://codereview.chromium.org/134753003/
> https://codereview.chromium.org/139743005/
> 
> BUG=240576, 246077
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166114

TBR=rbyers@chromium.org,esprehn@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=240576, 246077

Review URL: https://codereview.chromium.org/134133004

git-svn-id: svn://svn.chromium.org/blink/trunk@166118 bbb929c8-8fbe-4397-9dbb-9b2b20218538