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

chrome/browser/password_manager/mock_password_store_service.cc

Index: chrome/browser/password_manager/mock_password_store_service.cc
diff --git a/chrome/browser/password_manager/mock_password_store_service.cc b/chrome/browser/password_manager/mock_password_store_service.cc
index 7ad2f2497ccd8f5db26a4fa01afa39bf869e98c3..b2e9b786d230b2a2f93985c1f6e7eb9b4e3e1edf 100644
--- a/chrome/browser/password_manager/mock_password_store_service.cc
+++ b/chrome/browser/password_manager/mock_password_store_service.cc
@@ -11,8 +11,7 @@ KeyedService* MockPasswordStoreService::Build(
     content::BrowserContext* /*profile*/) {
   scoped_refptr<password_manager::PasswordStore> store(
       new password_manager::MockPasswordStore);
-  if (!store.get() ||
-      !store->Init(syncer::SyncableService::StartSyncFlare(), ""))
+  if (!store.get() || !store->Init(syncer::SyncableService::StartSyncFlare()))
     return NULL;
   return new MockPasswordStoreService(store);
 }