Roll third_party/externals/swiftshader 1c462ebc904c..a27dfcf868bf (3 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/1c462ebc904c..a27dfcf868bf

git log 1c462ebc904c..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
2019-10-14 digit@google.com [linux]: Remove linux namespace.

Created with:
  gclient setdep -r third_party/externals/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-skia-autoroll
Please CC csmartdalton@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=skia.primary:Test-Debian9-Clang-GCE-GPU-SwiftShader-x86_64-Debug-All-SwiftShader
Bug: None
TBR=csmartdalton@google.com
Change-Id: I63aad6ded03d8133addc83119f1b79d47faebc1a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/248732
Reviewed-by: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
1 file changed