Roll src/third_party/skia ac29f1342fd2..df9071f57626 (3 commits)

https://skia.googlesource.com/skia.git/+log/ac29f1342fd2..df9071f57626

git log ac29f1342fd2..df9071f57626 --date=short --first-parent --format='%ad %ae %s'
2019-12-23 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src 1c1af9fc..bd5c3742 (425 commits)
2019-12-23 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 fe2ed33a56dd..07d3bcf1c443 (10 commits)
2019-12-23 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 6d29348ddb7e..6e3a387c0159 (4 commits)

Created with:
  gclient setdep -r src/third_party/skia@df9071f57626

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 fmalita@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: fmalita@google.com
Change-Id: I062a358a0a18a5d763aabf95605f593fc7b74122
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1980453Reviewed-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@{#727148}

DEPS

@@ -175,7 +175,7 @@ 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': 'ac29f1342fd2dbf4928b204680edffbe20ae617c',
+  'skia_revision': 'df9071f5762622fe132352dda29bf15240bac300',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.