Enable display lists.

Change-Id: Id0d9b987251da5b7ecbb5497a55dbb5937430316
diff --git a/core/java/android/view/ViewRoot.java b/core/java/android/view/ViewRoot.java
index 2e368b8..06261bb 100644
--- a/core/java/android/view/ViewRoot.java
+++ b/core/java/android/view/ViewRoot.java
@@ -561,6 +561,11 @@
             scheduleTraversals();
         }
     }
+    
+    void invalidate() {
+        mDirty.set(0, 0, mWidth, mHeight);
+        scheduleTraversals();
+    }
 
     public ViewParent getParent() {
         return null;