Add chromeos-amd64-generic-dbg as an optional builder to commit-queue.cfg

This CL adds chromeos-amd64-generic-dbg to commit-queue.cfg to run
when	changes are applied to content/gpu and media/. This is because
these two libraries include files which utilize the 'use_vaapi' guard.

Bug: 1007498
Change-Id: I3579624f6ad2d26989e30c1080d248428c9c751b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1830113Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701350}

docs/infra/cq_builders.md

@@ -127,6 +127,12 @@ builder.
     * [`//third_party/blink/renderer/platform/graphics/gpu/.+`](https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/graphics/gpu/)
     * [`//ui/gl/.+`](https://cs.chromium.org/chromium/src/ui/gl/)
 
+* [chromeos-amd64-generic-dbg](https://ci.chromium.org/p/chromium/builders/luci.chromium.try/chromeos-amd64-generic-dbg) ([`commit-queue.cfg` entry](https://cs.chromium.org/search/?q=package:%5Echromium$+file:commit-queue.cfg+chromium/try/chromeos-amd64-generic-dbg)) ([matching builders](https://cs.chromium.org/search/?q=file:trybots.py+chromeos-amd64-generic-dbg))
+
+  Path regular expressions:
+    * [`//content/gpu/.+`](https://cs.chromium.org/chromium/src/content/gpu/)
+    * [`//media/.+`](https://cs.chromium.org/chromium/src/media/)
+
 * [chromeos-kevin-compile-rel](https://ci.chromium.org/p/chromium/builders/luci.chromium.try/chromeos-kevin-compile-rel) ([`commit-queue.cfg` entry](https://cs.chromium.org/search/?q=package:%5Echromium$+file:commit-queue.cfg+chromium/try/chromeos-kevin-compile-rel)) ([matching builders](https://cs.chromium.org/search/?q=file:trybots.py+chromeos-kevin-compile-rel))
 
   Path regular expressions:

infra/config/commit-queue.cfg

@@ -193,6 +193,12 @@ config_groups {
         location_regexp: ".+/[+]/third_party/blink/renderer/platform/graphics/gpu/.+"
         location_regexp: ".+/[+]/ui/gl/.+"
       }
+      builders {
+        name: "chromium/try/chromeos-amd64-generic-dbg"
+        location_regexp: ".+/[+]/content/gpu/.+"
+        location_regexp: ".+/[+]/media/.+"
+
+      }
       builders {
         name: "chromium/try/chromeos-kevin-compile-rel"
         location_regexp: ".+/[+]/chromeos/CHROMEOS_LKGM"