Revert "Revert "[BR07.1] Expose setDataSaverEnabled from Connect..."

Revert submission 2799494-revert-2745215-npmsbpf-OBOPDXREUI

Reason for revert: Need to 1. Merge API first. 2. Wait for prebuilt. 3. Merge the caller.

Reverted changes: /q/submissionid:2799494-revert-2745215-npmsbpf-OBOPDXREUI

Change-Id: Icd5f3d40595a0d2a221b016cec70568bf3597c16
diff --git a/common/flags.aconfig b/common/flags.aconfig
index 2e552a1..7235202 100644
--- a/common/flags.aconfig
+++ b/common/flags.aconfig
@@ -20,3 +20,10 @@
   description: "Remove expired services from MdnsServiceCache"
   bug: "304649384"
 }
+
+flag {
+  name: "set_data_saver_via_cm"
+  namespace: "android_core_networking"
+  description: "Set data saver through ConnectivityManager API"
+  bug: "297836825"
+}