Roll src/third_party/angle a44d96dcd676..20b1259ae94e (3 commits)

https://chromium.googlesource.com/angle/angle.git/+log/a44d96dcd676..20b1259ae94e

git log a44d96dcd676..20b1259ae94e --date=short --first-parent --format='%ad %ae %s'
2020-02-05 jmadill@chromium.org Vulkan: Command graph linearization (Step 2).
2020-02-05 jonahr@google.com Extend ANGLE_iosurface_client_buffer to Vulkan backend for Swangle
2020-02-05 julien.isorce@chromium.org Move generic code from rx::DisplayAndroid/Ozone to rx::DisplayEGL

Created with:
  gclient setdep -r src/third_party/angle@20b1259ae94e

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 cnorthrop@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: chromium:1015454
Tbr: cnorthrop@google.com
Change-Id: I65d1f64f148ad9167dff326e3a4a2d3785e71a02
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2040014Reviewed-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@{#738782}

DEPS

@@ -188,7 +188,7 @@ 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': 'a44d96dcd676fc7d446b41fb766caad9bdab9fda',
+  'angle_revision': '20b1259ae94e522a48ff43bd05f75b82b8fa9703',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.