GuestView: Lazily push attributes to the browser process on attach

extensions/renderer/resources/guest_view/web_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 37 matching lines @@
           createDefaultApiMethod(apiMethods[i]);
     }
   }
 
   // Forward proto.foo* method calls to WebViewImpl.foo*.
   GuestViewContainer.forwardApiMethods(proto, apiMethods);
 };
 
 // Initiates navigation once the <webview> element is attached to the DOM.
 WebViewImpl.prototype.onElementAttached = function() {
+  // Mark all attributes as dirty on attachment.
+  for (var i in this.attributes) {
+    this.attributes[i].dirty = true;
+  }
   for (var i in this.attributes) {
     this.attributes[i].attach();
   }
 };
 
 // Resets some state upon detaching <webview> element from the DOM.
 WebViewImpl.prototype.onElementDetached = function() {
   this.guest.destroy();
   for (var i in this.attributes) {
+    this.attributes[i].dirty = false;
+  }
+  for (var i in this.attributes) {
     this.attributes[i].detach();
   }
 };
 
 // Sets the <webview>.request property.
 WebViewImpl.prototype.setRequestPropertyOnWebViewElement = function(request) {
   Object.defineProperty(
       this.element,
       'request',
       {
@@ skipping 83 matching lines @@
 };
 
 WebViewImpl.prototype.onAttach = function(storagePartitionId) {
   this.attributes[WebViewConstants.ATTRIBUTE_PARTITION].setValueIgnoreMutation(
       storagePartitionId);
 };
 
 WebViewImpl.prototype.buildContainerParams = function() {
   var params = { 'userAgentOverride': this.userAgentOverride };
   for (var i in this.attributes) {
-    params[i] = this.attributes[i].getValue();
+    var value = this.attributes[i].getValueIfDirty();
+    if (value)
+      params[i] = value;
   }
   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.
   if (opt_guestInstanceId) {
     if (this.guest.getId() == opt_guestInstanceId) {
       return true;
@@ skipping 30 matching lines @@
   }.bind(this));
 };
 
 // Implemented when the ChromeWebView API is available.
 WebViewImpl.prototype.maybeSetupContextMenus = function() {};
 
 GuestViewContainer.registerElement(WebViewImpl);
 
 // Exports.
 exports.WebViewImpl = WebViewImpl;