Roll Skia from 3000d6b8c25c to 21efb7c7ddbc (7 revisions)

https://skia.googlesource.com/skia.git/+log/3000d6b8c25c..21efb7c7ddbc

2020-08-04 michaelludwig@google.com Fix inversion unit test
2020-08-04 jlavrova@google.com Chromium Project Code Inclusion
2020-08-04 brianosman@google.com Revert "Revert "Revert "Put top level FPs into their own functions"""
2020-08-04 jvanverth@google.com Reland "Revise GrMtlGpu::onUpdateBackendTexture."
2020-08-04 borenet@google.com Revert "[recipes] Verify that we actually deleted the file/dir on android"
2020-08-04 michaelludwig@google.com Fix inversion tracking across simplifies in GrShape
2020-08-04 borenet@google.com [recipes] Verify that we actually deleted the file/dir on android

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 herb@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: herb@google.com
Change-Id: Ibfae48ea8ba0c4c25ec591741f5ce7bb563d06e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2336898Reviewed-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@{#794648}

DEPS

@@ -195,7 +195,7 @@ 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': '3000d6b8c25cd8505fa309b51fd32cf80c513732',
+  'skia_revision': '21efb7c7ddbc911adb60228934c0cdf14085f0ce',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.