Enable "chromium.resultdb.result_sink" experiment on chromium ci builders at 10%

This experiment has been enabled at 100% on fyi builders and it's confirmed working.

Bug: 1108016
Change-Id: Ie421701de49116dab4169a6e210d069e01bbba37
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2476536Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Chan Li <chanli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817729}

infra/config/lib/ci.star

@@ -339,6 +339,7 @@ def ci_builder(
         tree_closing = False,
         notifies = None,
         resultdb_bigquery_exports = None,
+        experiments = None,
         **kwargs):
     """Define a CI builder.
 
@@ -393,6 +394,11 @@ def ci_builder(
     ]
     merged_resultdb_bigquery_exports.extend(resultdb_bigquery_exports or [])
 
+    if not experiments or experiments.get("chromium.resultdb.result_sink") == None:
+        # Enable "chromium.resultdb.result_sink" on all ci builders for 10% by default.
+        experiments = experiments or {}
+        experiments["chromium.resultdb.result_sink"] = 10
+
     # Define the builder first so that any validation of luci.builder arguments
     # (e.g. bucket) occurs before we try to use it
     builders.builder(
@@ -400,6 +406,7 @@ def ci_builder(
         branch_selector = branch_selector,
         resultdb_bigquery_exports = merged_resultdb_bigquery_exports,
         notifies = notifies,
+        experiments = experiments,
         **kwargs
     )