For instance, in the case of a ScriptContext,
the extension_object() getter fails.

Change-Id: Id0d65bc7c44438f60e2e824535081fa785feb3c8
Reviewed-on: https://chromium-review.googlesource.com/c/1454482Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59365}