[Password Manager] Setup experiment to restrict autofilling of sync credential

chrome/browser/password_manager/sync_metrics.cc

Index: chrome/browser/password_manager/sync_metrics.cc
diff --git a/chrome/browser/password_manager/sync_metrics.cc b/chrome/browser/password_manager/sync_metrics.cc
index 4eddf427ccd22db327b2fa421aaee66bd509056d..08c2626853879be6b639630f865fa8fd0d5c53a7 100644
--- a/chrome/browser/password_manager/sync_metrics.cc
+++ b/chrome/browser/password_manager/sync_metrics.cc
@@ -14,10 +14,20 @@
 namespace password_manager_sync_metrics {
 
 std::string GetSyncUsername(Profile* profile) {
+  // If sync is set up, return early if we aren't syncing passwords.
+  if (ProfileSyncServiceFactory::HasProfileSyncService(profile)) {
+    ProfileSyncService* sync_service =
+        ProfileSyncServiceFactory::GetForProfile(profile);
+    if (!sync_service->HasSyncSetupCompleted() ||
+        !sync_service->GetActiveDataTypes().Has(syncer::PASSWORDS))
+      return std::string();
+  }
+
   SigninManagerBase* signin_manager =
       SigninManagerFactory::GetForProfile(profile);
+
   if (!signin_manager)
-    return "";
+    return std::string();
 
   return signin_manager->GetAuthenticatedUsername();
 }