Roll Skia from f3087d8297fe to b7e836cee99b (4 revisions)

https://skia.googlesource.com/skia.git/+log/f3087d8297fe..b7e836cee99b

2021-01-19 mtklein@google.com Revert "Support indexing by loop variables in SkVMGenerator"
2021-01-19 bsalomon@google.com Reland "Test all YUVA image factories with different encoded origins."
2021-01-19 brianosman@google.com Support indexing by loop variables in SkVMGenerator
2021-01-19 csmartdalton@google.com Extract some GrPathTessellatoOp logic into virtual helper classes

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/+doc/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
Cq-Do-Not-Cancel-Tryjobs: true
Bug: None
Tbr: scroggo@google.com
Change-Id: I9d52bbdffdc4c0547f4d4c8fc6163b8e2d1fdc3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2638555Reviewed-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@{#844977}

DEPS

@@ -199,7 +199,7 @@ 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': 'f3087d8297feb2478849f4a2e69f367da6ceb779',
+  'skia_revision': 'b7e836cee99b981882c2523bfe293e95cff51942',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.