Stop using sublayer transform in blink

Turns out that this is no longer necessary.

I will remove the sublayer transform methods from the WebLayer API in a follow up CL (since this will have to be coordinated with chromium changes).

BUG=None

Review URL: https://codereview.chromium.org/78233009

git-svn-id: svn://svn.chromium.org/blink/trunk@167228 bbb929c8-8fbe-4397-9dbb-9b2b20218538