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

Change-Id: I76215a48e76234501b7ce253dedfa449502ab88f
diff --git a/src/com/android/launcher2/LauncherModel.java b/src/com/android/launcher2/LauncherModel.java
index 713268a..7e72610 100644
--- a/src/com/android/launcher2/LauncherModel.java
+++ b/src/com/android/launcher2/LauncherModel.java
@@ -492,6 +492,9 @@
                 mLoaderTask.stopLocked();
             }
         }
+        mItems.clear();
+        mAppWidgets.clear();
+        mFolders.clear();
     }
 
     /**