Upload metrics for Linux Devicelab Test Drone

This is a reland of https://flutter-review.googlesource.com/c/infra/+/33380.

With https://flutter-review.googlesource.com/c/recipes/+/33440, the failure like https://ci.chromium.org/ui/p/flutter/builders/prod/Linux_build_test%20flutter_gallery__transition_perf/26/overview should be fixed.

This CL is a no-op, as the builder is with `bringup: true`. I will validate the logics before enabling it in prod.

Change-Id: Id9414f1d0b6bf9560527ac653a65bfdc2cb65627
Bug: https://github.com/flutter/flutter/issues/103542
Reviewed-on: https://flutter-review.googlesource.com/c/infra/+/33500
Commit-Queue: Keyong Han <keyonghan@google.com>
Reviewed-by: Yusuf Mohsinally <mohsinally@google.com>
diff --git a/config/flutter_config.star b/config/flutter_config.star
index d8867e0..ccc2c5d 100644
--- a/config/flutter_config.star
+++ b/config/flutter_config.star
@@ -97,6 +97,8 @@
         caches = ci_yaml.legacy_swarming_caches(ci_yaml_config, None, "linux_android"),
         dimensions = {"device_type": "msm8952"},
         os = platform_properties["linux_android"]["os"],
+        # Uploads metrics only for master/main branches, where prefix is empty.
+        properties = {"upload_metrics": True} if not prefix else {},
     )
     common.mac_prod_builder(
         name = "%sMac SDK Drone" % prefix,
diff --git a/config/generated/flutter/luci/cr-buildbucket.cfg b/config/generated/flutter/luci/cr-buildbucket.cfg
index a8adfb8..9662208 100644
--- a/config/generated/flutter/luci/cr-buildbucket.cfg
+++ b/config/generated/flutter/luci/cr-buildbucket.cfg
@@ -669,6 +669,7 @@
         '  "goma_jobs": "200",'
         '  "mastername": "client.flutter",'
         '  "recipe": "devicelab/devicelab_test_drone",'
+        '  "upload_metrics": true,'
         '  "upload_packages": true'
         '}'
       execution_timeout_secs: 3600