Roll third_party/externals/swiftshader b9f03f47d5f5..31916f494c2e (7 commits)

https://swiftshader.googlesource.com/SwiftShader.git/+log/b9f03f47d5f5..31916f494c2e

git log b9f03f47d5f5..31916f494c2e --date=short --first-parent --format='%ad %ae %s'
2019-12-07 digit@google.com [Subzero] Remove assert that breaks Shuffle operations.
2019-12-06 bclayton@google.com SpirvShader: Use struct for MemoryVisitor callback.
2019-12-06 bclayton@google.com Regres: Update dEQP to include fence timeout fix.
2019-12-06 bclayton@google.com Vulkan: Tidy VkCommandBuffer.cpp
2019-12-06 bclayton@google.com Reactor: Rename Blend() to Shuffle()
2019-12-06 swiftshader.regress@gmail.com Regres: Update test lists @ b9f03f47
2019-12-06 bclayton@google.com Reactor: Switch swizzles over to 16-bit hex codes

Created with:
  gclient setdep -r third_party/externals/swiftshader@31916f494c2e

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 djsollen@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/skia.primary:Test-Debian9-Clang-GCE-GPU-SwiftShader-x86_64-Debug-All-SwiftShader
Bug: None
Tbr: djsollen@google.com
Change-Id: I4935d6eb318cfcba021a1688eb764d9ef9be6fa9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/258778
Reviewed-by: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>

Author: skia-autoroll

DEPS

@@ -31,7 +31,7 @@ deps = {
   "third_party/externals/spirv-cross"     : "https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Cross@53ab2144b90abede33be5161aec5dfc94ddc3caf",
   "third_party/externals/spirv-headers"   : "https://skia.googlesource.com/external/github.com/KhronosGroup/SPIRV-Headers.git@29c11140baaf9f7fdaa39a583672c556bf1795a1",
   "third_party/externals/spirv-tools"     : "https://skia.googlesource.com/external/github.com/KhronosGroup/SPIRV-Tools.git@0c4feb643b89d1792b02f7cbef315e9d95633bd7",
-  "third_party/externals/swiftshader"     : "https://swiftshader.googlesource.com/SwiftShader@b9f03f47d5f552905f1003ada49729240a7ca2c4",
+  "third_party/externals/swiftshader"     : "https://swiftshader.googlesource.com/SwiftShader@31916f494c2eca2ee3257733812ce21aa8f2e756",
   #"third_party/externals/v8"              : "https://chromium.googlesource.com/v8/v8.git@5f1ae66d5634e43563b2d25ea652dfb94c31a3b4",
   "third_party/externals/wuffs"           : "https://skia.googlesource.com/external/github.com/google/wuffs.git@4080840928c0b05a80cda0d14ac2e2615f679f1a",
   "third_party/externals/zlib"            : "https://chromium.googlesource.com/chromium/src/third_party/zlib@47af7c547f8551bd25424e56354a2ae1e9062859",