Separating methods for updating the model to a sepatate class.

Removing static access to model update methods, to allow for better
access control and testing

Change-Id: I9afe004dbf1b2fe50df422fd28bceea9230a4704

src/com/android/launcher3/model/UserLockStateChangedTask.java

@@ -95,7 +95,7 @@ public class UserLockStateChangedTask extends ExtendedModelTask {
         }
         bindUpdatedShortcuts(updatedShortcutInfos, deletedShortcutInfos, mUser);
         if (!deletedShortcutInfos.isEmpty()) {
-            LauncherModel.deleteItemsFromDatabase(context, deletedShortcutInfos);
+            getModelWriter().deleteItemsFromDatabase(deletedShortcutInfos);
         }
 
         // Remove shortcut id map for that user