[Password Manager] Add UMA stats for custom passphrase users.

chrome/browser/password_manager/test_password_store_service.cc

Index: chrome/browser/password_manager/test_password_store_service.cc
diff --git a/chrome/browser/password_manager/test_password_store_service.cc b/chrome/browser/password_manager/test_password_store_service.cc
index 209c4ad8f9f20e68a313f1d0fb3ce491d8a9820a..2c5ef82ea6017994d7c9a0bb3465605f39d96e3d 100644
--- a/chrome/browser/password_manager/test_password_store_service.cc
+++ b/chrome/browser/password_manager/test_password_store_service.cc
@@ -12,7 +12,7 @@ KeyedService* TestPasswordStoreService::Build(
   scoped_refptr<password_manager::PasswordStore> store(
       new password_manager::TestPasswordStore);
   if (!store.get() ||
-      !store->Init(syncer::SyncableService::StartSyncFlare(), ""))
+      !store->Init(syncer::SyncableService::StartSyncFlare()))
     return NULL;
   return new TestPasswordStoreService(store);
 }