Fixing bug 5011917 - clearing refernce to old folders from FolderInfo

-> Also, ensured that unbind() gets called on all ItemInfos on rotate

Change-Id: I869b68fcae5c66702ec204596f5ecabdc7a32df7
diff --git a/src/com/android/launcher2/ItemInfo.java b/src/com/android/launcher2/ItemInfo.java
index 3a1c29a..8d46624 100644
--- a/src/com/android/launcher2/ItemInfo.java
+++ b/src/com/android/launcher2/ItemInfo.java
@@ -144,7 +144,13 @@
             values.put(LauncherSettings.Favorites.ICON, data);
         }
     }
-    
+
+    /**
+     * It is very important that sub-classes implement this if they contain any references
+     * to the activity (anything in the view hierarchy etc.). If not, leaks can result since
+     * ItemInfo objects persist across rotation and can hence leak by holding stale references
+     * to the old view hierarchy / activity.
+     */
     void unbind() {
     }