Allow previous view hierarchy to be GC'ed more quickly on rotation

Change-Id: I76215a48e76234501b7ce253dedfa449502ab88f
diff --git a/src/com/android/launcher2/PagedViewWithDraggableItems.java b/src/com/android/launcher2/PagedViewWithDraggableItems.java
index f24d7e0..3f72292 100644
--- a/src/com/android/launcher2/PagedViewWithDraggableItems.java
+++ b/src/com/android/launcher2/PagedViewWithDraggableItems.java
@@ -150,4 +150,10 @@
     public void setDragSlopeThreshold(float dragSlopeThreshold) {
         mDragSlopeThreshold = dragSlopeThreshold;
     }
+
+    @Override
+    protected void onDetachedFromWindow() {
+        mLastTouchedItem = null;
+        super.onDetachedFromWindow();
+    }
 }