Migrate chromeos-amd64-generic-rel to builderfull.

crrev.com/i/3444414 allocates the machines for this.

Bug: 1140727
Change-Id: Id49c7c2ad4f6c692fef2b1bcbdc87ba50d2ee602
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2572400Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833433}

infra/config/generated/cr-buildbucket.cfg

@@ -27083,12 +27083,11 @@ buckets {
       name: "chromeos-amd64-generic-rel"
       swarming_host: "chromium-swarm.appspot.com"
       swarming_tags: "vpython:native-python-wrapper"
-      dimensions: "builderless:1"
+      dimensions: "builder:chromeos-amd64-generic-rel"
       dimensions: "cores:8"
       dimensions: "cpu:x86-64"
       dimensions: "os:Ubuntu-16.04"
       dimensions: "pool:luci.chromium.try"
-      dimensions: "ssd:0"
       exe {
         cipd_package: "infra/recipe_bundles/chromium.googlesource.com/chromium/tools/build"
         cipd_version: "refs/heads/master"

infra/config/subprojects/chromium/try.star

@@ -649,6 +649,7 @@ try_.chromium_chromiumos_builder(
 try_.chromium_chromiumos_builder(
     name = "chromeos-amd64-generic-rel",
     branch_selector = branches.ALL_BRANCHES,
+    builderless = not settings.is_master,
     main_list_view = "try",
     tryjob = try_.job(),
 )