Roll src/third_party/dawn 9b45b5aafa37..b6d7c5370888 (2 commits)

https://dawn.googlesource.com/dawn.git/+log/9b45b5aafa37..b6d7c5370888

git log 9b45b5aafa37..b6d7c5370888 --date=short --no-merges --format='%ad %ae %s'
2019-08-13 shaobo.yan@intel.com Reland "Fix dynamic buffer offset issues on D3D12 backend"
2019-08-13 enga@chromium.org Factor RenderPass command validation

Created with:
  gclient setdep -r src/third_party/dawn@b6d7c5370888

The AutoRoll server is located here: https://autoroll.skia.org/r/dawn-chromium-autoroll

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


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
TBR=cwallez@google.com

Bug: None
Change-Id: I2f0fe8c3ec78b88166b603b5529546d21fdcd796
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1750887Reviewed-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@{#686399}

DEPS

@@ -280,7 +280,7 @@ 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': '9b45b5aafa377817ea1af1aadccfe44598d8ec68',
+  'dawn_revision': 'b6d7c537088835c386bc7850d85300f9f72d4cf6',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.