Roll src/third_party/swiftshader 814779132a6f..b6c572d0b111 (2 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/814779132a6f..b6c572d0b111

git log 814779132a6f..b6c572d0b111 --date=short --no-merges --format='%ad %ae %s'
2019-09-07 bclayton@google.com Revert "Migrate from yarn to marl."
2019-09-07 bclayton@google.com Migrate from yarn to marl.

Created with:
  gclient setdep -r src/third_party/swiftshader@b6c572d0b111

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

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

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

CQ_INCLUDE_TRYBOTS=luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_chromium_msan_rel_ng;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
TBR=swiftshader-team+autoroll@google.com

Bug: chromium:b/140546382
Change-Id: I33ae4810e2a92d8a9ac75771e3632bd501d7d3f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1790973Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#694560}

DEPS

@@ -178,7 +178,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.
-  'swiftshader_revision': '814779132a6f14effd3e50f1ff697a3d1b4f341d',
+  'swiftshader_revision': 'b6c572d0b1114e0159d742e8d89bc3609cf59bef',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.