Prevent flicker when starting a drag.

Also, animate item the view to its new position when dragging.
diff --git a/src/com/android/launcher2/Folder.java b/src/com/android/launcher2/Folder.java
index 018b284..cb450b9 100644
--- a/src/com/android/launcher2/Folder.java
+++ b/src/com/android/launcher2/Folder.java
@@ -108,13 +108,19 @@
         return true;
     }
 
+    @Override
     public void setDragController(DragController dragController) {
         mDragController = dragController;
     }
 
+    @Override
     public void onDropCompleted(View target, boolean success) {
     }
 
+    @Override
+    public void onDragViewVisible() {
+    }
+
     /**
      * Sets the adapter used to populate the content area. The adapter must only
      * contains ShortcutInfo items.