Roll src/third_party/skia 3fafc831bc15..7b55818248cc (6 commits)

https://skia.googlesource.com/skia.git/+log/3fafc831bc15..7b55818248cc

git log 3fafc831bc15..7b55818248cc --date=short --no-merges --format='%ad %ae %s'
2019-11-15 jvanverth@google.com Add flag to Viewer to trigger continuous redraw.
2019-11-15 robertphillips@google.com Revert "Reland "Reland "Reland "Implement sample mask and sample locations support in Vulkan""""
2019-11-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 1b52f05868c9..5f4db6a76640 (9 commits)
2019-11-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src 7ca6de3a..69610187 (8341 commits)
2019-11-15 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/swiftshader b2407dd746de..102fd19c65f4 (4 commits)
2019-11-15 csmartdalton@google.com Reland "Reland "Reland "Implement sample mask and sample locations support in Vulkan"""

Created with:
  gclient setdep -r src/third_party/skia@7b55818248cc

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 halcanary@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
TBR=halcanary@google.com

Bug: chromium:None,chromium:None,chromium:None
Change-Id: I1cfe2ee7fbbfb46ae9817d8ebcc54328a800677c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1919259Reviewed-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@{#715684}

DEPS

@@ -172,7 +172,7 @@ 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': '3fafc831bc15c7a456a9726ca129610017e24cde',
+  'skia_revision': '7b55818248cc497669b3574ca161c52f4b1d5ea8',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.