This makes escape analysis skip analyzing the code entry field within
JSFunction objects. Said field is an untagged pointer field and hence
cannot be tracked by an ObjectState node.

R=jarin@chromium.org
TEST=mjsunit/regress/regress-crbug-613494
BUG=chromium:613494

Review-Url: https://codereview.chromium.org/1997353002
Cr-Commit-Position: refs/heads/master@{#36436}