Show prelogin only once

 Bug: 5081641

Change-Id: I1c625e3528de9a7cd37dae5b8b428ff141759e14
diff --git a/res/xml/debug_preferences.xml b/res/xml/debug_preferences.xml
index 5126b0d..1fc4f4c 100644
--- a/res/xml/debug_preferences.xml
+++ b/res/xml/debug_preferences.xml
@@ -76,4 +76,8 @@
         android:title="@string/js_engine_flags"
         android:singleLine="true" />
 
+    <Preference
+        android:key="reset_prelogin"
+        android:title="@string/pref_development_reset_prelogin" />
+
 </PreferenceScreen>