Enable ResizeObserver

Promotes ResizeObserver to stable

Intent to ship: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/z6ienONUb5A

LGTM1 from dglazgov, LGTM2 from foolip, LGTM3 from chrishtr on Oct 17

Bug: 612962
Change-Id: I3dc59fd0ab725acc6f40bf5a3bbd70de5e889f0f
Reviewed-on: https://chromium-review.googlesource.com/754562
Commit-Queue: Aleks Totic <atotic@chromium.org>
Reviewed-by: Yoav Weiss <yoav@yoav.ws>
Cr-Commit-Position: refs/heads/master@{#515203}
2 files changed