Expose the LauncherModel ModelDelegate

Added a getter for LauncherModel's ModelDelegate.

bug: 184179894
Test: manual
Change-Id: I94d2ee535f7c96e0d3672f053f32f55ddd10cba0
diff --git a/src/com/android/launcher3/LauncherModel.java b/src/com/android/launcher3/LauncherModel.java
index 699495c..eef3980 100644
--- a/src/com/android/launcher3/LauncherModel.java
+++ b/src/com/android/launcher3/LauncherModel.java
@@ -130,6 +130,10 @@
         mModelDelegate = ModelDelegate.newInstance(context, app, mBgAllAppsList, mBgDataModel);
     }
 
+    public ModelDelegate getModelDelegate() {
+        return mModelDelegate;
+    }
+
     /**
      * Adds the provided items to the workspace.
      */