Revert r175934 "Accelerate small canvases if Ganesh is on."

The problem with this patch is it is attempting to determine if we are
gpu rasterized by querying the compositor but compositing state may not yet
be initialized at the time the canvas is used, or may never be initialized
in some cases. This is just conceptually broken and needs to be addressed
with a different approach that doesn't query the compositor.

TBR=abarth@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/343273002

git-svn-id: svn://svn.chromium.org/blink/trunk@176654 bbb929c8-8fbe-4397-9dbb-9b2b20218538