Roll src/third_party/dawn 3ded65e8072e..6f92b9160b19 (2 commits)

https://dawn.googlesource.com/dawn.git/+log/3ded65e8072e..6f92b9160b19

git log 3ded65e8072e..6f92b9160b19 --date=short --first-parent --format='%ad %ae %s'
2020-03-02 natlee@microsoft.com Also use ExternalImageDescriptor in D3D12 and Metal Backends
2020-03-02 rharrison@chromium.org Rolling 4 dependencies

Created with:
  gclient setdep -r src/third_party/dawn@6f92b9160b19

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: chromium:1036080
Tbr: cwallez@google.com
Change-Id: I75b1bdf2abc9152cea69548741172bb781d335b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2083859Reviewed-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@{#746219}

DEPS

@@ -302,7 +302,7 @@ 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': '3ded65e8072e0cdccd0d0edebccffde37d4428b0',
+  'dawn_revision': '6f92b9160b197ba49b084faa7764f865b0c9ea92',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.