[Password Manager] Add UMA stats to track interaction with synced accounts.

components/password_manager/core/browser/password_store.cc

Index: components/password_manager/core/browser/password_store.cc
diff --git a/components/password_manager/core/browser/password_store.cc b/components/password_manager/core/browser/password_store.cc
index 2605f85621ca409e7185391560957037312a13f2..9710bca729371bdd230f6c2c35d617ac5be39a46 100644
--- a/components/password_manager/core/browser/password_store.cc
+++ b/components/password_manager/core/browser/password_store.cc
@@ -78,8 +78,9 @@ PasswordStore::PasswordStore(
       observers_(new ObserverListThreadSafe<Observer>()),
       shutdown_called_(false) {}
 
-bool PasswordStore::Init(const syncer::SyncableService::StartSyncFlare& flare) {
-  ReportMetrics();
+bool PasswordStore::Init(const syncer::SyncableService::StartSyncFlare& flare,
+                         const std::string& sync_username) {
+  ReportMetrics(sync_username);
 #if defined(PASSWORD_MANAGER_ENABLE_SYNC)
   ScheduleTask(base::Bind(&PasswordStore::InitSyncableService, this, flare));
 #endif
@@ -162,8 +163,9 @@ void PasswordStore::GetBlacklistLogins(PasswordStoreConsumer* consumer) {
   Schedule(&PasswordStore::GetBlacklistLoginsImpl, consumer);
 }
 
-void PasswordStore::ReportMetrics() {
-  ScheduleTask(base::Bind(&PasswordStore::ReportMetricsImpl, this));
+void PasswordStore::ReportMetrics(const std::string& sync_username) {
+  ScheduleTask(base::Bind(&PasswordStore::ReportMetricsImpl, this,
+                          sync_username));
 }
 
 void PasswordStore::AddObserver(Observer* observer) {