Roll src/third_party/angle f87fac56d22f..4b7bac78a9ea (3 commits)

https://chromium.googlesource.com/angle/angle.git/+log/f87fac56d22f..4b7bac78a9ea

git log f87fac56d22f..4b7bac78a9ea --date=short --first-parent --format='%ad %ae %s'
2020-02-18 jmadill@chromium.org Vulkan: Throttle when way ahead of device.
2020-02-18 jmadill@chromium.org Vulkan: Command graph linearization for SemaphoreVk.
2020-02-18 lexa.knyazev@gmail.com Move sampleAlphaToCoverage out of blendState

Created with:
  gclient setdep -r src/third_party/angle@4b7bac78a9ea

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 cwallez@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: cwallez@google.com
Change-Id: I9d353c87c0d620af2f276f806f7e70eb40d50191
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2062799Reviewed-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@{#742318}

DEPS

@@ -183,7 +183,7 @@ 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': 'f87fac56d22fd859c4c5879b9a7d59abc20cf4f1',
+  'angle_revision': '4b7bac78a9eab3a6ed4fb2815a2d0e42cb3586e4',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.