Remove ownership aruments from render target wrap functions

Remove ownership aruments from render target wrap functions

We never adopt render targets (just borrow them).

BUG=skia:

Change-Id: Ie899b814a7a81339a8735bbd7ad9facc66e580d7
Reviewed-on: https://skia-review.googlesource.com/9525
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>