The information that such functions must be parsed in module mode
didn't get properly propagated.

Also refactor some related code to make it more robust. In particular,
set parsing_module_ at parser construction time only.

Bug: v8:1569, v8:6919
Change-Id: Id136fb15c240373cad07c82025b778d0c0c43148
Reviewed-on: https://chromium-review.googlesource.com/716478
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48811}