Custom wrap constructor overloads.

Follow up on crrev.com/206793006 and also call wrap() in the code generated
for a particular constructor overloading when [Custom=Wrap] is in effect
for one or more constructors.

R=nbarth@chromium.org,haraken@chromium.org
BUG=338804

Review URL: https://codereview.chromium.org/209893002

git-svn-id: svn://svn.chromium.org/blink/trunk@169839 bbb929c8-8fbe-4397-9dbb-9b2b20218538