Roll Dawn from 6298d2b70cb6 to a7278454b28b (3 revisions)

https://dawn.googlesource.com/dawn.git/+log/6298d2b70cb6..a7278454b28b

2020-10-15 cwallez@chromium.org Make dawn_use_x11 = use_x11 when building inside Chromium
2020-10-15 cwallez@chromium.org ShaderModule: Don't use Format::Type for reflection.
2020-10-15 cwallez@chromium.org TextureView: only store the Aspect as a bitfield.

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 enga@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: chromium:976495
Tbr: enga@google.com
Change-Id: I27c267e5cbb2504cac33252275070e1538238ead
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2475010Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#817531}

DEPS

@@ -323,7 +323,7 @@ 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': '6298d2b70cb67bb929f7817f2186f618ec8f1ca1',
+  'dawn_revision': 'a7278454b28bafb72ff557cf3e087a8fb94de909',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.