Roll src/third_party/skia 8969a1641bec..c21316a73b54 (8 commits)

https://skia.googlesource.com/skia.git/+log/8969a1641bec..c21316a73b54

git log 8969a1641bec..c21316a73b54 --date=short --first-parent --format='%ad %ae %s'
2020-01-07 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 1031d2c65b5e..51e653f03f26 (10 commits)
2020-01-07 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 10a900e5ffaf..068dd89cab31 (7 commits)
2020-01-07 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src 3beaf136..55a27186 (337 commits)
2020-01-07 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2020-01-07 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2020-01-07 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2020-01-07 mtklein@google.com handle unpremul in skvm blitter
2020-01-07 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).

Created with:
  gclient setdep -r src/third_party/skia@c21316a73b54

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-autoroll
Please CC jvanverth@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-blink-rel;luci.chromium.try:linux-chromeos-compile-dbg;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Bug: None
Tbr: jvanverth@google.com
Change-Id: I74f36ec10311dd765809d67db72a9ef573eda41f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1988764Reviewed-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@{#728828}

DEPS

@@ -181,7 +181,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and whatever else without interference from each other.
-  'skia_revision': '8969a1641beced679ea5981e57d59103e1786330',
+  'skia_revision': 'c21316a73b543f0cba5d115d5bed81852d432190',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.