Expose workspace.moveToDefaultScreen.

This is to allow derived launcher classes to move the workspace to the
default screen when a drag is started, in case the current screen is not
capable of acting as a drop target.

Bug: 13962574
Change-Id: I8a6e94ce08be825c344beb708d244d2def5f319f

src/com/android/launcher3/Launcher.java

@@ -4567,6 +4567,10 @@ public class Launcher extends Activity
         return new ShortcutInfo(shortcutIntent, caption, icon);
     }
 
+    protected void moveWorkspaceToDefaultScreen() {
+        mWorkspace.moveToDefaultScreen(false);
+    }
+
     public void startDrag(View dragView, ItemInfo dragInfo, DragSource source) {
         dragView.setTag(dragInfo);
         mWorkspace.onDragStartedWithItem(dragView);