When re-scoping arrow function parameter initializers, temporaries
should be moved from the closure of the old scope to the closure of
the new scope, if necessary.

R=adamk@chromium.org, rossberg@chromium.org
BUG=chromium:622663
LOG=N

Review-Url: https://codereview.chromium.org/2083083007
Cr-Commit-Position: refs/heads/master@{#37335}