ok, plumb in GrContextFactory

ok, plumb in GrContextFactory

Didn't know what options would be useful here (path renderers?), so I've
left them default.  Obviously we can thread them through TestSrc options.

I now have "841 ok" and no failures on my Linux laptop, though I imagine
the GPU tests are all just no-op'd by the TODO at the bottom of the file.

Change-Id: Id934c0bdb5de96d96f2a391106b5d20116f41979
Reviewed-on: https://skia-review.googlesource.com/10213
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>