Refactor to accept coordinator allowlist in feature param

Instead of specify explicitly for AWS and GCP, it's more extensible to
accept coordinator allowlist in the feature param. This also allows
coverage in the interop tests which can override the allowlist.

Change-Id: Ib0fb47205e0b7a9b1a5004df06e89678495c372d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5444731
Reviewed-by: Andrew Paseltiner <[email protected]>
Reviewed-by: Dominic Farolino <[email protected]>
Reviewed-by: Alex Turner <[email protected]>
Commit-Queue: Nan Lin <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1290765}
diff --git a/components/aggregation_service/features.h b/components/aggregation_service/features.h
index f08cc65..2f42dff 100644
--- a/components/aggregation_service/features.h
+++ b/components/aggregation_service/features.h
@@ -16,13 +16,14 @@
 COMPONENT_EXPORT(AGGREGATION_SERVICE)
 BASE_DECLARE_FEATURE(kAggregationServiceMultipleCloudProviders);
 
+// Comma-separated origins. The first origin will be used as default. When
+// empty, the default coordinator origins will be used.
+//
+// TODO(linnan): Consider replacing this with a command-line switch since it
+// isn't needed in production.
 COMPONENT_EXPORT(AGGREGATION_SERVICE)
 extern const base::FeatureParam<std::string>
-    kAggregationServiceCoordinatorAwsCloud;
-
-COMPONENT_EXPORT(AGGREGATION_SERVICE)
-extern const base::FeatureParam<std::string>
-    kAggregationServiceCoordinatorGcpCloud;
+    kAggregationServiceCoordinatorAllowlist;
 
 }  // namespace aggregation_service