Roll Tint from c55fc39acb to 6857ed0b0b (1 revision)

https://dawn.googlesource.com/tint.git/+log/c55fc39acba8..6857ed0b0bc3

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/tint-dawn
Please CC rharrison@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

Bug: None
Tbr: rharrison@google.com
Change-Id: Idc9f5356ca0bcac57fdc5201f32a159ce1f7bd9f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/31287
Reviewed-by: <dawn-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: <dawn-autoroll@skia-public.iam.gserviceaccount.com>

DEPS

@@ -90,7 +90,7 @@ deps = {
 
   # WGSL support
   'third_party/tint': {
-    'url': '{dawn_git}/tint@c55fc39acba826308cfb7c8c2bbf010c232e3224',
+    'url': '{dawn_git}/tint@6857ed0b0bc33e5a12b69cdab999f9e4e3795233',
     'condition': 'dawn_standalone',
   },