Automatically add linux-headless-shell-rel for changes under headless/

It shouldn't be to expensive given low volume of changes under headless/,
yet should be quite handy to minimize the number of downstream bot
failures.

Change-Id: Iec090e797b489f758ef5791541aca51591f3191d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4298379
Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1111821}

infra/config/generated/cq-builders.md

@@ -335,6 +335,11 @@ builder.
   * [`//chrome/browser/ui/webui/ash/chromebox_for_meetings/.+`](https://cs.chromium.org/chromium/src/chrome/browser/ui/webui/ash/chromebox_for_meetings/)
   * [`//chrome/test/data/webui/chromeos/chromebox_for_meetings/.+`](https://cs.chromium.org/chromium/src/chrome/test/data/webui/chromeos/chromebox_for_meetings/)
 
+* [linux-headless-shell-rel](https://ci.chromium.org/p/chromium/builders/try/linux-headless-shell-rel) ([definition](https://cs.chromium.org/search?q=+file:/try/.*\.star$+""linux-headless-shell-rel""))
+
+  Location filters:
+  * [`//headless/.+`](https://cs.chromium.org/chromium/src/headless/)
+
 * [linux-perfetto-rel](https://ci.chromium.org/p/chromium/builders/try/linux-perfetto-rel) ([definition](https://cs.chromium.org/search?q=+file:/try/.*\.star$+""linux-perfetto-rel""))
 
   Location filters:

infra/config/generated/cq-usage/full.cfg

@@ -1575,6 +1575,31 @@ config_groups {
           path_regexp: "infra/config/generated/builders/try/linux-chromeos-rel/.+"
         }
       }
+      builders {
+        name: "chromium/try/linux-headless-shell-rel"
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "headless/.+"
+        }
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "docs/.+"
+          exclude: true
+        }
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "infra/config/.+"
+          exclude: true
+        }
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "infra/config/generated/builders/try/linux-headless-shell-rel/.+"
+        }
+      }
       builders {
         name: "chromium/try/linux-lacros-rel"
         location_filters {

infra/config/generated/luci/commit-queue.cfg

@@ -2521,7 +2521,28 @@ config_groups {
       }
       builders {
         name: "chromium/try/linux-headless-shell-rel"
-        includable_only: true
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "headless/.+"
+        }
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "docs/.+"
+          exclude: true
+        }
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "infra/config/.+"
+          exclude: true
+        }
+        location_filters {
+          gerrit_host_regexp: ".*"
+          gerrit_project_regexp: ".*"
+          path_regexp: "infra/config/generated/builders/try/linux-headless-shell-rel/.+"
+        }
       }
       builders {
         name: "chromium/try/linux-inverse-fieldtrials-fyi-rel"

infra/config/subprojects/chromium/try/tryserver.chromium.linux.star

@@ -124,6 +124,11 @@ try_.builder(
     name = "linux-headless-shell-rel",
     mirrors = ["ci/linux-headless-shell-rel"],
     reclient_jobs = reclient.jobs.LOW_JOBS_FOR_CQ,
+    tryjob = try_.job(
+        location_filters = [
+            "headless/.+",
+        ],
+    ),
 )
 
 try_.builder(