Turn on layer squashing and turn off the overlap map if --enable-bleeding-edge-rendering-fast-paths is true.

BUG=

Review URL: https://codereview.chromium.org/175833002

git-svn-id: svn://svn.chromium.org/blink/trunk@167825 bbb929c8-8fbe-4397-9dbb-9b2b20218538