Add support for [Constructor, Custom=Wrap]

Adds support for constructors when there's a custom wrap.

This is split off as 2/2 bindings-only change from:
Implement ImageData constructors.
https://codereview.chromium.org/196343032/

Follow-up to:
Use wrapper_configuration consistently in bindings
https://codereview.chromium.org/199633014/

R=haraken
BUG=338804

Review URL: https://codereview.chromium.org/206793006

git-svn-id: svn://svn.chromium.org/blink/trunk@169835 bbb929c8-8fbe-4397-9dbb-9b2b20218538