Roll src/third_party/swiftshader 74d3f371f201..3cfba7f05be4 (2 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/74d3f371f201..3cfba7f05be4

git log 74d3f371f201..3cfba7f05be4 --date=short --first-parent --format='%ad %ae %s'
2020-02-20 sugoi@google.com Revert "VK_EXT_shader_stencil_export support"
2020-02-20 sugoi@google.com VK_EXT_shader_stencil_export support

Created with:
  gclient setdep -r src/third_party/swiftshader@3cfba7f05be4

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: I96f168f531234543a96e93a20e36c479fac9201e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067129Reviewed-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@{#743228}

DEPS

@@ -187,7 +187,7 @@ 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': '74d3f371f2015deeedb985a8b24ba242ea65caef',
+  'swiftshader_revision': '3cfba7f05be4a68edb53fe1faca764c678bec4f5',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.