Roll SwiftShader from a681d12639f4 to 12c9d4ac61f2 (3 revisions)

https://swiftshader.googlesource.com/SwiftShader.git/+log/a681d12639f4..12c9d4ac61f2

2020-07-27 sugoi@google.com Manual changes required for SPIR-V update
2020-07-27 sugoi@google.com Merge changes Icf7b69da,I2c88ee38
2020-07-27 sugoi@google.com Merge changes Id54668de,I200b4417

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/+doc/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;luci.chromium.try:linux-swangle-try-x64;luci.chromium.try:win-swangle-try-x86
Bug: None
Tbr: swiftshader-team+autoroll@google.com
Change-Id: Id8a4515c73cee45835b5005bb8830a6556ba19e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321259Reviewed-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@{#792101}

DEPS

@@ -211,7 +211,7 @@ 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': 'a681d12639f484359556db9ca30a6dd7033377d8',
+  'swiftshader_revision': '12c9d4ac61f26e787dfe4ea256b2e1b8fa35e040',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.