Escape analysis will eliminate the context, if possible. Materialization
must then ensure that the materialized object has the right map, and that
the context register is set accordingly.

R=jarin@chromium.org
BUG=569530,v8:4586
LOG=n

Review URL: https://codereview.chromium.org/1572293002

Cr-Commit-Position: refs/heads/master@{#33201}