Roll src/third_party/angle a8acd7799b44..273f9c7c26d7 (4 commits)

https://chromium.googlesource.com/angle/angle.git/+log/a8acd7799b44..273f9c7c26d7

git log a8acd7799b44..273f9c7c26d7 --date=short --first-parent --format='%ad %ae %s'
2020-03-17 angle-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/SwiftShader 3a50a43df988..440fc9959f06 (1 commits)
2020-03-17 angle-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/glslang/src 9b620aa0c12d..4b2483ee88ab (1 commits)
2020-03-17 angle-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/vulkan-validation-layers/src be663d752e45..6cd8cbdaab99 (7 commits)
2020-03-17 angle-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/vulkan-loader/src f1d9f12a19de..64c36933d4f2 (2 commits)

Created with:
  gclient setdep -r src/third_party/angle@273f9c7c26d7

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 courtneygo@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: 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
Bug: None
Tbr: courtneygo@google.com
Change-Id: I8cef478b73d2f55c23a1a6738b9899986e713dcc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2107257Reviewed-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@{#750909}

DEPS

@@ -187,7 +187,7 @@ 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': 'a8acd7799b4490fe484e36e6db3ed60f4a97072f',
+  'angle_revision': '273f9c7c26d701f4a9953594d15753f8a5d88538',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.