Roll Skia from 33c64a447368 to 20fad3206488 (7 revisions)

https://skia.googlesource.com/skia.git/+log/33c64a447368..20fad3206488

2020-12-23 brianosman@google.com SkSL: Hide most integral types from runtime effects
2020-12-23 brianosman@google.com SkSL: Remove many unused sampler types
2020-12-23 brianosman@google.com SkSL: Hide non-square (half) matrices from runtime effects
2020-12-23 fmalita@chromium.org Add rsx_blob_shader GM
2020-12-23 reed@google.com Use bitmap.asImage()
2020-12-23 reed@google.com Work on hiding filter-quality
2020-12-23 brianosman@google.com SkSL: Remove all $gsamplerFoo types

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 bungeman@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: bungeman@google.com
Change-Id: I2876283ee04bfb56f43f91e8c396e98177ea3623
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2600581Reviewed-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@{#839176}

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': '33c64a447368a5cbae2f9a383ab0c066465fae52',
+  'skia_revision': '20fad3206488f7fd571010789f1ac730e6817ea0',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.