Rewrite returns in derived constructors to only replace undefined with
this, and otherwise just return the value, and let the construct stub
builtin throw an exception if the result is a primitive instead of a
JSReceiver.

R=yangguo@chromium.org
TBR=marja@chromium.org
BUG=chromium:706642

Review-Url: https://codereview.chromium.org/2788033002
Cr-Commit-Position: refs/heads/master@{#44288}