<webview>, <appview> and <extensionoptions> can run in a detached state.

extensions/renderer/resources/guest_view/web_view.js

 // Copyright (c) 2012 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.
 
 // This module implements WebView (<webview>) as a custom element that wraps a
 // BrowserPlugin object element. The object element is hidden within
 // the shadow DOM of the WebView element.
 
 var DocumentNatives = requireNative('document_natives');
 var GuestView = require('guestView').GuestView;
@@ skipping 56 matching lines @@
 WebViewImpl.prototype.onElementAttached = function() {
   this.attributes[WebViewConstants.ATTRIBUTE_SRC].parse();
 };
 
 // Resets some state upon detaching <webview> element from the DOM.
 WebViewImpl.prototype.onElementDetached = function() {
   this.guest.destroy();
   this.beforeFirstNavigation = true;
   this.attributes[WebViewConstants.ATTRIBUTE_PARTITION].validPartitionId =
       true;
-  this.internalInstanceId = 0;
 };
 
 // Sets the <webview>.request property.
 WebViewImpl.prototype.setRequestPropertyOnWebViewElement = function(request) {
   Object.defineProperty(
       this.element,
       'request',
       {
         value: request,
         enumerable: true
@@ skipping 59 matching lines @@
       newHeight <= maxHeight)) {
     element.style.width = newWidth + 'px';
     element.style.height = newHeight + 'px';
     // Only fire the DOM event if the size of the <webview> has actually
     // changed.
     this.dispatchEvent(webViewEvent);
   }
 };
 
 WebViewImpl.prototype.createGuest = function() {
-  var params = {
-    'instanceId': this.viewInstanceId,
-    'userAgentOverride': this.userAgentOverride,
-    'width': this.element.offsetWidth,
-    'height': this.element.offsetHeight,
-  };
-  for (var i in this.attributes) {
-    params[i] = this.attributes[i].getValue();
-  }
-
-  this.guest.create(params, function() {
+  this.guest.create(this.buildParams(), function() {
     this.attachWindow();
   }.bind(this));
 };
 
 WebViewImpl.prototype.onFrameNameChanged = function(name) {
   name = name || '';
   if (name === '') {
     this.element.removeAttribute(WebViewConstants.ATTRIBUTE_NAME);
   } else {
     this.attributes[WebViewConstants.ATTRIBUTE_NAME].setValue(name);
@@ skipping 40 matching lines @@
     this.attributes[WebViewConstants.ATTRIBUTE_SRC].setValueIgnoreMutation(
         newValue);
   }
 };
 
 WebViewImpl.prototype.onAttach = function(storagePartitionId) {
   this.attributes[WebViewConstants.ATTRIBUTE_PARTITION].setValue(
       storagePartitionId);
 };
 
-WebViewImpl.prototype.buildAttachParams = function() {
+WebViewImpl.prototype.buildContainerParams = function() {
   var params = { 'userAgentOverride': this.userAgentOverride };
   for (var i in this.attributes) {
     params[i] = this.attributes[i].getValue();
   }
   return params;
 };
 
 WebViewImpl.prototype.attachWindow = function(opt_guestInstanceId) {
   // If |opt_guestInstanceId| was provided, then a different existing guest is
   // being attached to this webview, and the current one will get destroyed.
@@ skipping 34 matching lines @@
 WebViewImpl.prototype.setupExperimentalContextMenus = function() {};
 WebViewImpl.prototype.maybeSetupExperimentalChromeWebViewEvents =
   function(request) {
     return request;
 };
 
 GuestViewContainer.registerElement(WebViewImpl);
 
 // Exports.
 exports.WebViewImpl = WebViewImpl;