Fix flippity GM for *ooprddl configs (take 2)

The flippity GM doesn't create backend textures but it does perform some custom proxy creation (i.e., using MakeTextureProxyFromData to set the origin) that requires a direct context. This work must be done in onGpuSetup but doesn't entail any fancy lifetime management.

TBR=egdaniel@google.com
Change-Id: I258c0cb66746ca6853a4e228e10407671d7d55d9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/297697
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
3 files changed