Roll Skia from 8670c9887529 to 15b4892925ba (10 revisions)

https://skia.googlesource.com/skia.git/+log/8670c9887529..15b4892925ba

2020-12-09 johnstiles@google.com Simplify constant single-value SkSL constructors.
2020-12-09 johnstiles@google.com Parenthesize intrinsic comparisons properly in Metal.
2020-12-09 bsalomon@google.com Rewrite restore_scissor_on_fbo_change
2020-12-09 johnstiles@google.com Fix SPIR-V compilation of binary expressions of boolN type.
2020-12-09 borenet@google.com [infra] Roll infra DEPS, update CIPD packages
2020-12-09 johnstiles@google.com Add newline to end of Metal's Globals struct definition.
2020-12-09 brianosman@google.com Remove fInputColor usage in unit-test FPs
2020-12-09 brianosman@google.com Remove modulation by input color in convolution FPs
2020-12-09 johnstiles@google.com Add $genHType version of inversesqrt.
2020-12-09 brianosman@google.com Increase Metal timeout to 1 second

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 jmbetancourt@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: chromium:1152831
Tbr: jmbetancourt@google.com
Change-Id: I1713a7837e204474e058e087cfbd14d2b86e5238
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2582141Reviewed-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@{#835288}

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': '8670c9887529e8241511b1e27be748975d4f61f0',
+  'skia_revision': '15b4892925ba9df656a92671d7b087e4d480a363',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.