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
diff --git a/src/com/android/launcher3/CellLayout.java b/src/com/android/launcher3/CellLayout.java
index da12e67..121b9fb 100644
--- a/src/com/android/launcher3/CellLayout.java
+++ b/src/com/android/launcher3/CellLayout.java
@@ -2144,7 +2144,7 @@
                 info.spanY = lp.cellVSpan;
 
                 if (requiresDbUpdate) {
-                    LauncherModel.modifyItemInDatabase(getContext(), info, container, screenId,
+                    mLauncher.getModelWriter().modifyItemInDatabase(info, container, screenId,
                             info.cellX, info.cellY, info.spanX, info.spanY);
                 }
             }