Roll third_party/externals/swiftshader 80c796becc43..b55772e6e7dd (2 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/80c796becc43..b55772e6e7dd


git log 80c796becc43..b55772e6e7dd --date=short --no-merges --format='%ad %ae %s'
2019-03-21 capn@google.com Use Kokoro configs/scripts for SwiftShader under tests/kokoro/ directory
2019-03-21 chrisforbes@google.com Remove remaining UBO & constants junk from DrawData


Created with:
  gclient setdep -r third_party/externals/swiftshader@b55772e6e7dd

The AutoRoll server is located here: https://autoroll.skia.org/r/swiftshader-skia-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.

CQ_INCLUDE_TRYBOTS=skia.primary:Test-Debian9-Clang-GCE-GPU-SwiftShader-x86_64-Debug-All-SwiftShader
TBR=brianosman@google.com

Change-Id: I377927db52395b3fac569324b9075766372cb282
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/202731
Reviewed-by: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>