[DevTools] Do not expose agents on Target

third_party/WebKit/Source/devtools/front_end/resources/AppManifestView.js

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 /**
  * @implements {SDK.SDKModelObserver<!SDK.ResourceTreeModel>}
  * @unrestricted
  */
 Resources.AppManifestView = class extends UI.VBox {
   constructor() {
     super(true);
@@ skipping 139 matching lines @@
       if (typeof value !== 'string')
         return '';
       return value;
     }
   }
 
   /**
    * @param {!Common.Event} event
    */
   _addToHomescreen(event) {
-    var target = SDK.targetManager.mainTarget();
-    if (target && target.hasBrowserCapability()) {
-      target.pageAgent().requestAppBanner();
+    var resourceTreeModel = SDK.targetManager.models(SDK.ResourceTreeModel)[0];
+    if (resourceTreeModel) {
+      resourceTreeModel.requestAppBanner();
       Common.console.show();
     }
   }
 };