Add debug option to disable performance features for testing

Change-Id: I508448907a83fb32028cb28eb64b72f97a863fd0
diff --git a/res/xml/debug_preferences.xml b/res/xml/debug_preferences.xml
index f23ce12..e244188 100644
--- a/res/xml/debug_preferences.xml
+++ b/res/xml/debug_preferences.xml
@@ -78,6 +78,14 @@
         android:defaultValue="false"
         android:title="@string/pref_development_nav_dump" />
 
+    <SwitchPreference
+        android:layout="@layout/swe_preference"
+        android:key="disable_perf"
+        android:defaultValue="true"
+        android:summaryOn="@string/pref_development_disable_perf_on"
+        android:summaryOff="@string/pref_development_disable_perf_off"
+        android:title="@string/pref_development_disable_perf" />
+
     <EditTextPreference
         android:layout="@layout/swe_preference"
         android:key="js_engine_flags"