Revert of Make all layout tests force composited (https://codereview.chromium.org/261143003/)

Reason for revert:
Breaks content_unittests that are unable to create graphics layers (likely similar to the FrameLoaderClientImplTest here).

Original issue's description:
> Make all layout tests force composited
> 
> BUG=361729
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=174049

TBR=esprehn@chromium.org,ojan@chromium.org,abarth@chromium.org,adamk@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=361729

Review URL: https://codereview.chromium.org/281393002

git-svn-id: svn://svn.chromium.org/blink/trunk@174052 bbb929c8-8fbe-4397-9dbb-9b2b20218538