Roll src/third_party/skia e6d31bd0894c..6e6b4dd7d3e2 (6 commits)

https://skia.googlesource.com/skia.git/+log/e6d31bd0894c..6e6b4dd7d3e2

git log e6d31bd0894c..6e6b4dd7d3e2 --date=short --first-parent --format='%ad %ae %s'
2019-12-19 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-12-19 jvanverth@google.com Revert "Generate small path SDFs directly from path."
2019-12-19 jvanverth@google.com Generate small path SDFs directly from path.
2019-12-19 bsalomon@google.com Revert "Revert "Blend functions as SkSL built ins.""
2019-12-19 reed@google.com Revert "temporarily expose postIDiv"
2019-12-19 jvanverth@google.com Add wireframe support to Metal.

Created with:
  gclient setdep -r src/third_party/skia@6e6b4dd7d3e2

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 borenet@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/+/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: borenet@google.com
Change-Id: I1ab721b51199c34fb8fd762c1ea77ec936ef729d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1976881Reviewed-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@{#726594}

DEPS

@@ -175,7 +175,7 @@ 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': 'e6d31bd0894c49e9c2f23b2c5160452030e6b2e2',
+  'skia_revision': '6e6b4dd7d3e20c698517ad193d47565eb1c803a5',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.