Revert "[graphite] Remember last snapped task for scratch devices"

This reverts commit bd6746e5de928ae73b288bc56e0b3d0f4197b233.

Reason for revert: breaking backdrop filter tests in chrome

Original change's description:
> [graphite] Remember last snapped task for scratch devices
>
> Change-Id: I3297b584fd48dc7151d4fff54218c1da2bbfcd5a
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/835576
> Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>

Change-Id: I697299e6c7e34355a934d8fc17593d6b3f29ccf8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/842917
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>
2 files changed