add fullscreen option

Change-Id: I88299c37a7e809492f806478f41365b56b2687be
diff --git a/src/com/android/browser/PreferenceKeys.java b/src/com/android/browser/PreferenceKeys.java
index 929339f..b4c4a68 100644
--- a/src/com/android/browser/PreferenceKeys.java
+++ b/src/com/android/browser/PreferenceKeys.java
@@ -76,6 +76,7 @@
     static final String PREF_ENABLE_QUICK_CONTROLS = "enable_quick_controls";
     static final String PREF_USE_MOST_VISITED_HOMEPAGE = "use_most_visited_homepage";
     static final String PREF_USE_INSTANT_SEARCH = "use_instant_search";
+    static final String PREF_FULLSCREEN = "fullscreen";
 
     // ----------------------
     // Keys for privacy_security_preferences.xml