Roll Skia from 70988bed1b3b to f6900c5b8439 (2 revisions) (#191481)

https://skia.googlesource.com/skia.git/+log/70988bed1b3b..f6900c5b8439

2026-08-21 thomsmit@google.com [graphite] Add sparse strips coverage
oracle
2026-08-21 skia-autoroll@skia-public.iam.gserviceaccount.com Roll
vulkan-deps from 71c3f1723099 to 3cc0a5d1905e (3 revisions)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC
awolff@google.com,kjlubick@google.com,robertphillips@google.com on the
revert to ensure that a human
is aware of the problem.

To file a bug in Skia: https://bugs.chromium.org/p/skia/issues/entry
To file a bug in Flutter:
https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md