[ios Mojo] Supporting code for define WebUI function.

ios/web/webui/resources/web_ui_module_load_notifier.js

+// Copyright 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.
+
+goog.provide('__crWeb.webUIModuleLoadNotifier');
+
+/**
+ * A holder class for require.js contexts whose load is pending.
+ * @constructor
+ */
+var WebUIModuleLoadNotifier = function() {
+  this.lastUsedId_ = 0;
+  this.pendingContexts_ = new Map();
+};
+
+/**
+ * Adds the given context to the list of pending contexts.
+ * @param {string} name Name of the module that will be loaded.
+ * @param {!Object} context Require.js context to hold.
+ * @return {string} Identifier for the added context, can be later used for
+ *     {@code moduleLoadCompleted} and {@code moduleLoadFailed} arguments.
+ */
+WebUIModuleLoadNotifier.prototype.addPendingContext = function(name, context) {
+  this.lastUsedId_++;
+  var key = name + this.lastUsedId_;
+  this.pendingContexts_.set(key, context);
+  return String(this.lastUsedId_);
+};
+
+/**
+ * Signals that module has successfully loaded.
+ * @param {string} name Name of the module that has been loaded.
+ * @param {String} loadId Identifier returned from {@code addPendingContext}.
+ */
+WebUIModuleLoadNotifier.prototype.moduleLoadCompleted = function(name, loadId) {
+  this.popContext_(name, loadId).completeLoad(name);
+};
+
+/**
+ * Signals that module has failed to load.
+ * @param {string} name Name of the module that has failed to load.
+ * @param {String} loadId Identifier returned from {@code addPendingContext}.
+ */
+WebUIModuleLoadNotifier.prototype.moduleLoadFailed = function(name, loadId) {
+  this.popContext_(name, loadId).onScriptFailure(name);
+};
+
+/**
+ * Pops the pending context.
+ * @param {string} name Name of the module that has failed to load.
+ * @param {String} loadId Identifier returned from {@code addPendingContext}.
+ * @return {Object} Require.js context
+ */
+WebUIModuleLoadNotifier.prototype.popContext_ = function(name, loadId) {
+  var key = name + loadId;
+  var context = this.pendingContexts_.get(key);
+  this.pendingContexts_.delete(key);
+  return context;
+};