Roll Skia from 6a204db32c49 to 7868692b9df0 (5 revisions)

https://skia.googlesource.com/skia.git/+log/6a204db32c49..7868692b9df0

2020-10-08 ethannicholas@google.com Moved SkSL VariableReference data into IRNode
2020-10-08 brianosman@google.com Remove inherited program element list (it's now unused)
2020-10-08 brianosman@google.com Put interface blocks into the intrinsic maps, too
2020-10-08 johnstiles@google.com Remove unused copy of DefinitionMap.
2020-10-08 kjlubick@google.com [canvaskit] Update quickstart to use 0.19.0

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 jvanverth@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: jvanverth@google.com
Change-Id: Iac4f37385bafcdaf799106100479a741d50d580b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461965Reviewed-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@{#815258}

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': '6a204db32c49af517bb475ee3ea07d06dce72203',
+  'skia_revision': '7868692b9df06325e0ee280024ed75f2eb5de95f',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.