Roll Dawn from e28cc55cac22 to c15c6eb9d8c3 (3 revisions)

https://dawn.googlesource.com/dawn.git/+log/e28cc55cac22..c15c6eb9d8c3

2020-07-16 cwallez@chromium.org dawn_wire/server: Use MapAsync to do Map[Read/Write]Async
2020-07-16 cwallez@chromium.org DawnTest: Use MapAsync for expectations.
2020-07-16 cwallez@chromium.org Roll third_party/swiftshader/ ad65826a2..e8dd233c7 (10 commits)

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/+doc/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: I920cff96b98bffd9c8d794a653f037556c3ce5b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2303096Reviewed-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@{#789187}

DEPS

@@ -317,7 +317,7 @@ 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': 'e28cc55cac223d727666fe2fa3c47daa147ee9ae',
+  'dawn_revision': 'c15c6eb9d8c37754c189d72b0f4add60cc499bd8',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.