Roll src/third_party/swiftshader fb632b91110c..a27dfcf868bf (2 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/fb632b91110c..a27dfcf868bf

git log fb632b91110c..a27dfcf868bf --date=short --no-merges --format='%ad %ae %s'
2019-10-14 digit@google.com Fix Linux build.
2019-10-14 digit@google.com [vulkan] Implement Linux-based external semaphore

Created with:
  gclient setdep -r src/third_party/swiftshader@a27dfcf868bf

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:140419396,chromium:b/140421726
Change-Id: Icd4b752a0fab65d56a76ba387b49a9aaadf231b9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860889Reviewed-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@{#705765}

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': 'fb632b91110cabce297c34b8c01ec8c931a10933',
+  'swiftshader_revision': 'a27dfcf868bf646d3ad6ea2f74d2ee9e3e4a3378',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.