infra/config: Add experimental bot to test patching on GClient.

Add linux_chromium_rel_ng_patch_on_gclient as an experimental builder at
5% to test that patching on GClient instead of bot_update works as
intended.

Bug: 643346
Change-Id: I6af85c344fff4e4d88c66b5e96872fbb90ffbb8d
Reviewed-on: https://chromium-review.googlesource.com/983012
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546706}

infra/config/branch/cq.cfg

@@ -117,6 +117,10 @@ verifiers {
         name: "linux_chromium_rel_ng"
         equivalent_to { bucket: "luci.chromium.try" percentage: 100 }
       }
+      builders {
+        name: "linux_chromium_rel_ng_patch_on_gclient"
+        experiment_percentage: 5
+      }
     }
     buckets {
       name: "master.tryserver.chromium.mac"

infra/config/global/cr-buildbucket.cfg

@@ -997,6 +997,16 @@ buckets {
       mixins: "goma-j150"
       name: "linux_chromium_rel_ng"
     }
+    builders {
+      mixins: "linux-try"
+      mixins: "goma-j150"
+      name: "linux_chromium_rel_ng_patch_on_gclient"
+      experimental: YES
+      recipe {
+        properties: "buildername:linux_chromium_rel_ng"
+        properties_j: "$depot_tools/bot_update:{\"apply_patch_on_gclient\":true}"
+      }
+    }
     builders { mixins: "linux-try" name: "linux_chromium_tsan_rel_ng" }
     builders { mixins: "linux-try" name: "linux_chromium_tsan_variable" }
     builders { mixins: "linux-try" name: "linux_chromium_ubsan_rel_ng" }