Implement a basic UI flow for cryptohome encryption migration.

chromeos/login/auth/login_performer.cc

Index: chromeos/login/auth/login_performer.cc
diff --git a/chromeos/login/auth/login_performer.cc b/chromeos/login/auth/login_performer.cc
index 6fa6aea3517f2e51e5cd76231a1f859b760ed89d..c4376c2979619846784963b3d593e88a3f8ecf18 100644
--- a/chromeos/login/auth/login_performer.cc
+++ b/chromeos/login/auth/login_performer.cc
@@ -107,11 +107,11 @@ void LoginPerformer::OnPasswordChangeDetected() {
   }
 }
 
-void LoginPerformer::OnOldEncryptionDetected() {
+void LoginPerformer::OnOldEncryptionDetected(const UserContext& user_context) {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
 
   if (delegate_)
-    delegate_->OnOldEncryptionDetected();
+    delegate_->OnOldEncryptionDetected(user_context);
   else
     NOTREACHED();
 }