Roll Skia from 6d0ab954e90c to 68e5f29d849a (4 revisions)

https://skia.googlesource.com/skia.git/+log/6d0ab954e90c..68e5f29d849a

2020-07-20 michaelludwig@google.com Keep a scratch block around for reuse in GrBlockAllocator
2020-07-20 jvanverth@google.com Avoid some unnecessary D3D state changes.
2020-07-20 mtklein@google.com remove stray weakref include
2020-07-20 brianosman@google.com Catch SkRuntimeEffects w/o "main" earlier

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
Bug: None
Tbr: robertphillips@google.com
Change-Id: I30e998a633cf96c6fab65b61b71766e7c8198153
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2309258Reviewed-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@{#790232}

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': '6d0ab954e90cb963c73dc84bbe7e9e3da54c19eb',
+  'skia_revision': '68e5f29d849a36edd9e9243dc05b88e4b288dd9b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.