Roll Skia from 41fc174d7967 to ec64d037bd04 (6 revisions)

https://skia.googlesource.com/skia.git/+log/41fc174d7967..ec64d037bd04

2020-10-15 mtklein@google.com cond_stack/mask_stack for CPU backend
2020-10-15 kjlubick@google.com [canvaskit] Expose Perlin Noise shaders.
2020-10-15 kjlubick@google.com [canvaskit] Clean up Shader docs/types/names
2020-10-15 adlai@google.com Migrate debugger & canvaskit to GrDirectContext
2020-10-15 bsalomon@google.com Ref GrDirectContext in MakeBackendRenderTargetSurface
2020-10-15 ethannicholas@google.com moved SkSL InterfaceBlock data into IRNode

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 robertphillips@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: robertphillips@google.com
Change-Id: I24dcaab427c4af24778f6a4944b79907e8e496f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2476566Reviewed-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@{#817632}

DEPS

@@ -200,7 +200,7 @@ 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': '41fc174d7967b85594fe8205a964d882fd1aea37',
+  'skia_revision': 'ec64d037bd0446bc1c48f711f11f7ca4ad911241',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.