Roll src/third_party/swiftshader 6fff5122a23e..a580e2d761c1 (2 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/6fff5122a23e..a580e2d761c1

git log 6fff5122a23e..a580e2d761c1 --date=short --no-merges --format='%ad %ae %s'
2019-10-04 capn@google.com Remove Vulkan project from Visual Studio solution
2019-10-04 pjackson@google.com Support LLVM 8+ with Reactor

Created with:
  gclient setdep -r src/third_party/swiftshader@a580e2d761c1

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/139189696,chromium:b/139412871
Change-Id: I88112da1f92eaa123bdf08088117958e38245e2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1841693Reviewed-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@{#702969}

DEPS

@@ -183,7 +183,7 @@ 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': '6fff5122a23e5f12ee546d0b2ea815cd4114af9a',
+  'swiftshader_revision': 'a580e2d761c1994a42e01866cfca5e318a67d12c',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.