Roll src/third_party/swiftshader 14b1e3f3d10a..c8974b38bff1 (6 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/14b1e3f3d10a..c8974b38bff1

git log 14b1e3f3d10a..c8974b38bff1 --date=short --first-parent --format='%ad %ae %s'
2020-03-27 bclayton@google.com Kokoro: Test LLVM 10 backend for ubuntu
2020-03-27 bclayton@google.com Coverage: Add 'turbo-cov': a faster reimplementation of llvm-cov
2020-03-27 capn@google.com Don't download all submodules for Kokoro tests
2020-03-27 bclayton@google.com Reactor: Disable more warnings to get LLVM 10 building
2020-03-27 bclayton@google.com LLVM 10: Add configs/common and configs/darwin.
2020-03-27 bclayton@google.com LLVM 10: Add configs/common and configs/linux.

Created with:
  gclient setdep -r src/third_party/swiftshader@c8974b38bff1

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
Bug: None
Tbr: swiftshader-team+autoroll@google.com
Change-Id: I69b285bc54d167bf17b5759d1fe531a3330276f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2123883Reviewed-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@{#754077}

DEPS

@@ -191,7 +191,7 @@ 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': '14b1e3f3d10a51254bc6b496037b2b62dc7efec9',
+  'swiftshader_revision': 'c8974b38bff1b64cc9f90376224fe1ef2353a254',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.