Roll src/third_party/skia 25cf469a112f..6c9b1fd6663e (10 commits)

https://skia.googlesource.com/skia.git/+log/25cf469a112f..6c9b1fd6663e

git log 25cf469a112f..6c9b1fd6663e --date=short --first-parent --format='%ad %ae %s'
2020-02-05 jvanverth@google.com Update Viewer docs for Android and iOS.
2020-02-05 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader 41a7302e9c62..8e8e1d0dd729 (4 commits)
2020-02-05 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 aa6dd50de0c5..58fc8b11cf3a (7 commits)
2020-02-05 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2020-02-04 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2020-02-04 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2020-02-04 egdaniel@google.com Make sure we invalidate mapped memory from vk transfer buffers before reading.
2020-02-04 tdenniston@google.com Revert "Initial checkin of GM verifier framework"
2020-02-04 tdenniston@google.com Initial checkin of GM verifier framework
2020-02-04 jvanverth@google.com Update iOS build instructions.

Created with:
  gclient setdep -r src/third_party/skia@6c9b1fd6663e

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 scroggo@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: scroggo@google.com
Change-Id: Ieeaf17a5514f142e6a145bc025f9fba4512d2265
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2038118Reviewed-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@{#738482}

DEPS

@@ -176,7 +176,7 @@ 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': '25cf469a112f1b125ef4900b0e14c48994ebc062',
+  'skia_revision': '6c9b1fd6663e683d5edbdab4c9ccd15c336746c3',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.