Prevent flicker when starting a drag.

Also, animate item the view to its new position when dragging.
diff --git a/src/com/android/launcher2/AllAppsPagedView.java b/src/com/android/launcher2/AllAppsPagedView.java
index 1f3df5f..4ca5b47 100644
--- a/src/com/android/launcher2/AllAppsPagedView.java
+++ b/src/com/android/launcher2/AllAppsPagedView.java
@@ -237,6 +237,10 @@
     }
 
     @Override
+    public void onDragViewVisible() {
+    }
+
+    @Override
     public void onDropCompleted(View target, boolean success) {
         // close the choice action mode if we have a proper drop
         if (target != this) {