Roll src/third_party/dawn 280b96ea8de3..af094e6a88d0 (2 commits)

https://dawn.googlesource.com/dawn.git/+log/280b96ea8de3..af094e6a88d0

git log 280b96ea8de3..af094e6a88d0 --date=short --first-parent --format='%ad %ae %s'
2019-12-11 sarahmashay@google.com Adding SPVC fuzzers
2019-12-11 bryan.bernhart@intel.com D3D12: Fix 64-bit overflow for large buffers and return OOM.

Created with:
  gclient setdep -r src/third_party/dawn@af094e6a88d0

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dawn-chromium-autoroll
Please CC cwallez@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:dawn-linux-x64-deps-rel;luci.chromium.try:dawn-mac-x64-deps-rel;luci.chromium.try:dawn-win10-x64-deps-rel;luci.chromium.try:dawn-win10-x86-deps-rel
Bug: None
Tbr: cwallez@google.com
Change-Id: Iec3f6ab6fb03ac0ae92363bfc5f14239c6a26dca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1963140Reviewed-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@{#724077}

DEPS

@@ -306,7 +306,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.
-  'dawn_revision': '280b96ea8de35e145be4878ca53b6eecf7f38e67',
+  'dawn_revision': 'af094e6a88d01073a4e5e15fa1b268a72bbb73aa',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.