Report PasswordStore metrics on iOS

On non-iOS platforms, the PasswordStore reports metrics about the
usage of password manager on every start. For iOS, all the pieces are
there, but have not been used.

This CL adds the reporting on iOS.

Bug: 887409
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: Icef32ced5cbc7e61776e0f1ca41466d4ef65f032
Reviewed-on: https://chromium-review.googlesource.com/1255523Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Vaclav Brozek <vabr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595773}

ios/chrome/browser/passwords/ios_chrome_password_manager_client.mm

@@ -7,6 +7,7 @@
 #include <memory>
 #include <utility>
 
+#include "base/no_destructor.h"
 #include "components/autofill/core/common/password_form.h"
 #include "components/browser_sync/profile_sync_service.h"
 #include "components/keyed_service/core/service_access_type.h"
@@ -15,6 +16,7 @@
 #include "components/password_manager/core/browser/password_manager.h"
 #include "components/password_manager/core/browser/password_manager_internals_service.h"
 #include "components/password_manager/core/browser/password_manager_util.h"
+#include "components/password_manager/core/browser/store_metrics_reporter.h"
 #include "components/password_manager/core/common/password_manager_pref_names.h"
 #include "components/signin/core/browser/signin_manager_base.h"
 #include "ios/chrome/browser/application_context.h"
@@ -62,6 +64,9 @@ IOSChromePasswordManagerClient::IOSChromePasswordManagerClient(
       helper_(this) {
   saving_passwords_enabled_.Init(
       password_manager::prefs::kCredentialsEnableService, GetPrefs());
+  static base::NoDestructor<password_manager::StoreMetricsReporter> reporter(
+      *saving_passwords_enabled_, this, GetSyncService(delegate_.browserState),
+      GetSigninManager(delegate_.browserState), GetPrefs());
   log_manager_ = password_manager::LogManager::Create(
       ios::PasswordManagerInternalsServiceFactory::GetForBrowserState(
           delegate_.browserState),