Roll ANGLE from 9912971cf9b3 to c75473c2cf88 (2 revisions)

https://chromium.googlesource.com/angle/angle.git/+log/9912971cf9b3..c75473c2cf88

2020-12-11 cclao@google.com Vulkan: Generalize FlipRotationSpecConst to SpecializationConstant
2020-12-10 courtneygo@google.com Vulkan: clean up comments, rename per request

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/angle-chromium-autoroll
Please CC syoussefi@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_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win-asan;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: syoussefi@google.com
Change-Id: I39373fcc2836421bb72fee250787427ddce3ca79
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586565Reviewed-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@{#836016}

DEPS

@@ -211,7 +211,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling ANGLE
   # and whatever else without interference from each other.
-  'angle_revision': '9912971cf9b3dc5f9890a2a2435031988624fdc7',
+  'angle_revision': 'c75473c2cf88b8068d77f2da4710c87aa08e06f9',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.