remove debug gl interface, grcontextfactory context type, and config.

Change-Id: I476d1066a227d70e39c1dd49220972fb4a075393
Reviewed-on: https://skia-review.googlesource.com/140788
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
23 files changed