Run Dawn DEPS trybots as experimental

This change runs Dawn DEPS trybots as experimental. It allows us to know
when Dawn changes will break Chromium and the autoroller. They are
experimental because we expect Chromium integration to break when Dawn's
API changes.

Bug: chromium:948902
Change-Id: Ifb2ac253fefc90c68a4b56d5895099e1ddf596e7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/6880
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kenneth Russell <kbr@google.com>
Commit-Queue: Austin Eng <enga@chromium.org>

infra/config/global/commit-queue.cfg

@@ -53,6 +53,27 @@ config_groups {
       builders {
         name: "chromium/try/win-dawn-rel"
       }
+
+      # Experimental builders
+      # These are experimental while Dawn's API is changing and we expect
+      # to break integration with Chromium
+      builders {
+        name: "chromium/try/dawn-linux-x64-deps-rel"
+        experiment_percentage: 100
+      }
+      builders {
+        name: "chromium/try/dawn-mac-x64-deps-rel"
+        experiment_percentage: 100
+      }
+      builders {
+        name: "chromium/try/dawn-win10-x64-deps-rel"
+        experiment_percentage: 100
+      }
+      builders {
+        name: "chromium/try/dawn-win10-x86-deps-rel"
+        experiment_percentage: 100
+      }
+
       retry_config {
         single_quota: 1
         global_quota: 2