compositor-worker: plumb element id and mutable properties

For proxied elements, this CL ensures that the element id and mutable
property bitfield are propagated to the compositor.

BUG=430155
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1405993008

Cr-Commit-Position: refs/heads/master@{#363737}
39 files changed