Roll external/skia f813ef7d1b74..9c23a9e790b2 (6 commits)

https://skia.googlesource.com/skia.git/+log/f813ef7d1b74..9c23a9e790b2

2019-08-11 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update SKP version
2019-08-11 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update Go deps
2019-08-10 robertphillips@google.com Revert "Initiate regeneration of mipmaps from proxy DAG land"
2019-08-10 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update Go deps
2019-08-10 csmartdalton@google.com Initiate regeneration of mipmaps from proxy DAG land
2019-08-09 senorblanco@chromium.org Dawn: remove a faulty assert.

The AutoRoll server is located here: https://skia-autoroll.corp.goog/r/android-master-autoroll

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

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

Test: Presubmit checks will test this change.
Change-Id: I8a10c13a24c8f46c9a4e54195d255027f0a012f9
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.