Fix bug with drag visualization and UserFolders.

When dragging an app shortcut, it was possible that we'd show a red rectangle
around a cell occupied by a UserFolder. This shouldn't be possible -- as soon
as that cell becomes the target drop cell, the folder should start handling
the drag and drop events.

Change-Id: I1b7a8b1aa9aeb7e2f1bd51ce8d947c06455e988f
diff --git a/src/com/android/launcher2/FolderIcon.java b/src/com/android/launcher2/FolderIcon.java
index 0013644..a09b6e0 100644
--- a/src/com/android/launcher2/FolderIcon.java
+++ b/src/com/android/launcher2/FolderIcon.java
@@ -102,4 +102,10 @@
             DragView dragView, Object dragInfo) {
         setCompoundDrawablesWithIntrinsicBounds(null, mCloseIcon, null, null);
     }
+
+    @Override
+    public DropTarget getDropTargetDelegate(DragSource source, int x, int y, int xOffset, int yOffset,
+            DragView dragView, Object dragInfo) {
+        return null;
+    }
 }