Oilpan: Remove GarbageCollected::ref/deref

Currently, if we use ref/deref in GarbageCollected objects, it will be asserted in runtime. Alternately, this CL changes it to compile error.

This is a change requested by mads.

Review URL: https://codereview.chromium.org/156033003

git-svn-id: svn://svn.chromium.org/blink/trunk@166989 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Unprefix -webkit-font-variant-ligatures

Feature dashboard link: http://www.chromestatus.com/features/5678497057996800

Intent-to-ship thread: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/2-JGOzPEnhU


BUG=342483

Review URL: https://codereview.chromium.org/157003004

git-svn-id: svn://svn.chromium.org/blink/trunk@166990 bbb929c8-8fbe-4397-9dbb-9b2b20218538