This CL replaces user_manager::UserID with AccountId.

components/user_manager/user_info_impl.cc

Index: components/user_manager/user_info_impl.cc
diff --git a/components/user_manager/user_info_impl.cc b/components/user_manager/user_info_impl.cc
index 6aa21a8adb71cf0d13822212cd78f55b3fb7542b..76417c8123f2fe3da628bafb71986c2650bb5f54 100644
--- a/components/user_manager/user_info_impl.cc
+++ b/components/user_manager/user_info_impl.cc
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
+#include "components/signin/core/account_id/account_id.h"
 
 namespace user_manager {
 
@@ -27,8 +28,8 @@ std::string UserInfoImpl::GetEmail() const {
   return "stub-user@domain.com";
 }
 
-std::string UserInfoImpl::GetUserID() const {
-  return GetEmail();
+AccountId UserInfoImpl::GetUserID() const {
+  return AccountId::FromUserEmail(GetEmail());
 }
 
 const gfx::ImageSkia& UserInfoImpl::GetImage() const {