Add a win-dawn-rel builder to be triggered from the Dawn CQ

This builder will run the dawn_end2end_tests on the GPU swarming bots
through the Chromium recipe.

BUG=chromium:901830

Change-Id: Ic943058c3b46119222509c6a435f0b83a305590f
Reviewed-on: https://chromium-review.googlesource.com/c/1325992
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608050}

infra/config/global/cr-buildbucket.cfg

@@ -279,6 +279,14 @@ builder_mixins {
   execution_timeout_secs: 72000 # 20h
 }
 
+builder_mixins {
+  name: "dawn-try"
+  service_account: "chromium-try-gpu-builder@chops-service-accounts.iam.gserviceaccount.com"
+  recipe {
+    properties: "mastername:tryserver.chromium.dawn"
+  }
+}
+
 builder_mixins {
   name: "fuzz-ci"
   recipe {
@@ -555,6 +563,12 @@ builder_mixins {
   }
 }
 
+builder_mixins {
+  name: "win-dawn-try"
+  mixins: "win"
+  mixins: "dawn-try"
+}
+
 builder_mixins {
   name: "win-gpu-ci"
   mixins: "win"
@@ -3231,6 +3245,7 @@ buckets {
       execution_timeout_secs: 14400 # 4h
     }
     builders { mixins: "win-try" name: "win_chromium_x64_rel_ng" }
+    builders { mixins: "win-dawn-try" name: "win-dawn-rel" }
     builders { mixins: "win-try" name: "win_mojo" }
     builders { mixins: "win-optional-gpu-try" name: "win_optional_gpu_tests_rel" }
     builders { mixins: "win-try" mixins: "upload_clang" name: "win_upload_clang" }