Fix documents for creating a GPU surface.

NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=5284

Change-Id: I9ca559576d9e7fdff612cfe79628303bc7677bd7
Reviewed-on: https://skia-review.googlesource.com/5284
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
1 file changed