reland: mash: Remove ChromeLauncherController's |id_to_item_controller_map_|.

chrome/browser/ui/ash/launcher/extension_app_window_launcher_controller.cc

Index: chrome/browser/ui/ash/launcher/extension_app_window_launcher_controller.cc
diff --git a/chrome/browser/ui/ash/launcher/extension_app_window_launcher_controller.cc b/chrome/browser/ui/ash/launcher/extension_app_window_launcher_controller.cc
index a0455ac1007fc47344d82bc6100bae6cd5086d8a..7db908150f4e010061d094d1303b4f5035dbd2c1 100644
--- a/chrome/browser/ui/ash/launcher/extension_app_window_launcher_controller.cc
+++ b/chrome/browser/ui/ash/launcher/extension_app_window_launcher_controller.cc
@@ -5,6 +5,7 @@
 #include "chrome/browser/ui/ash/launcher/extension_app_window_launcher_controller.h"
 
 #include "ash/shelf/shelf_delegate.h"
+#include "ash/shelf/shelf_model.h"
 #include "ash/shell.h"
 #include "ash/wm/window_properties.h"
 #include "ash/wm/window_util.h"
@@ -194,7 +195,8 @@ void ExtensionAppWindowLauncherController::RegisterApp(AppWindow* app_window) {
         item_controller->set_image_set_by_controller(true);
       }
     } else {
-      owner()->SetShelfItemDelegate(shelf_id, std::move(controller));
+      ash::ShelfModel* shelf_model = ash::Shell::Get()->shelf_model();
+      shelf_model->SetShelfItemDelegate(shelf_id, std::move(controller));
     }
 
     // We need to change the controller associated with app_shelf_id.