Roll src/third_party/skia 9378b8016c60..4f17b60208fa (2 commits)

https://skia.googlesource.com/skia.git/+log/9378b8016c60..4f17b60208fa

git log 9378b8016c60..4f17b60208fa --date=short --first-parent --format='%ad %ae %s'
2020-04-13 zmo@chromium.org Use Dawn's BUILD.gn instead of defining another one for Skia.
2020-04-13 reed@google.com [skvm] approx_atan2

Created with:
  gclient setdep -r src/third_party/skia@4f17b60208fa

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 kjlubick@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: chromium:1064305
Tbr: kjlubick@google.com
Change-Id: Id015a8ce1118a8ec6099d4bafaff190d179e6101
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2148202Reviewed-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@{#758667}

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': '9378b8016c60473de8f31ad747e30f42a318911a',
+  'skia_revision': '4f17b60208fa022309ecce72b99bacf942f5ca09',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.