Inverted lab preference

Change-Id: I28636302e00a23ee65e2c63e5ebe4bebdc4576c4
diff --git a/src/com/android/browser/PreferenceKeys.java b/src/com/android/browser/PreferenceKeys.java
index 08ee91f..4174732 100644
--- a/src/com/android/browser/PreferenceKeys.java
+++ b/src/com/android/browser/PreferenceKeys.java
@@ -77,6 +77,7 @@
     static final String PREF_ENABLE_QUICK_CONTROLS = "enable_quick_controls";
     static final String PREF_USE_INSTANT_SEARCH = "use_instant_search";
     static final String PREF_FULLSCREEN = "fullscreen";
+    static final String PREF_INVERTED = "inverted";
 
     // ----------------------
     // Keys for privacy_security_preferences.xml