Remove legacy GrContext factories function and supporting code/types.

Change-Id: I437a4a0a58bf70ea1b8b0659b099a2af2bfa64fe
Reviewed-on: https://skia-review.googlesource.com/116197
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
23 files changed