Ensure that effect outputs from nodes are used if they have
an effect output. This helps us avoid an easy-to-make error
where we fail to update the effect chain with the result of
effectful operations.

Bug: v8:6929
Change-Id: I585dc627b3c330006ec04717ff9b2f5060dbad6a
Reviewed-on: https://chromium-review.googlesource.com/718107
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48861}