Reland "[graphite] SurfaceDrawContext -> DrawContext"

This reverts commit 9602a4fad0ef7072232351ffd1e6ab1b658fe359.

Reason for revert: fixed var ref

Original change's description:
> Revert "[graphite] SurfaceDrawContext -> DrawContext"
>
> This reverts commit a525fd141bbde7c226f98c223d4b59d064189220.
>
> Reason for revert: missed updating sdc->dc in one spot
>
> Original change's description:
> > [graphite] SurfaceDrawContext -> DrawContext
> >
> > Bug: skia:12466
> > Change-Id: If4a06bc0ab8befab8a155276c316ba9378b90a48
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/455658
> > Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> > Reviewed-by: Robert Phillips <robertphillips@google.com>
>
> Bug: skia:12466
> Change-Id: I60e316225d44d7046bc82c80fe42345d8941f99e
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/455662
> Auto-Submit: Michael Ludwig <michaelludwig@google.com>
> Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>

Bug: skia:12466
Change-Id: I693b1e39fd65fe20cd5bb3f36bcc5f3da011c6b3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/455663
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
Auto-Submit: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
8 files changed