It expected its argument to be a JSFunction, but fuzzer tests can
pass anything. Non-JSFunction arguments should just silently be
ignored, just like similar CF-whitelisted runtime functions do.

Bug: chromium:754177
Change-Id: I41b29528bbe72f24b3d84f021b22602160769d26
Reviewed-on: https://chromium-review.googlesource.com/610706Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47316}