Roll ANGLE from 39b777c6f00f to 257b9ad9fed6 (1 revision)

https://chromium.googlesource.com/angle/angle.git/+log/39b777c6f00f..257b9ad9fed6

2020-10-30 syoussefi@chromium.org Add a perf test for scissored draw calls

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 geofflang@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: geofflang@google.com
Change-Id: I054afd2ea55f395af36871f0a12d7d802b363625
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2509352Reviewed-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@{#822589}

DEPS

@@ -218,7 +218,7 @@ 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': '39b777c6f00fdb03804d7c27bb430307caca329c',
+  'angle_revision': '257b9ad9fed699743d41ec90afd52b72f485873b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.