fix tab switcher and menu

Change-Id: Ibcda8fc9fa73f11dba7d8f2f8061740910cedc55
diff --git a/src/com/android/browser/PhoneUi.java b/src/com/android/browser/PhoneUi.java
index 99320b7..9e3310b 100644
--- a/src/com/android/browser/PhoneUi.java
+++ b/src/com/android/browser/PhoneUi.java
@@ -263,4 +263,12 @@
         return false;
     }
 
+    public void toggleNavScreen() {
+        if (mNavScreen == null) {
+            showNavScreen();
+        } else {
+            hideNavScreen(false);
+        }
+    }
+
 }