Show an error dialog if Chrome Web Store widget fails to load

components/chrome_apps/webstore_widget/cws_widget/cws_widget_container.js

 // Copyright 2015 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.
 
 /**
  * CWSWidgetContainer contains a Chrome Web Store widget that displays list of
  * apps that satisfy certain constraints (e.g. fileHandler apps that can handle
  * files with specific file extension or MIME type) and enables the user to
  * install apps directly from it.
  * CWSWidgetContainer implements client side of the widget, which handles
@@ skipping 351 matching lines @@
  * handle showing the Chrome Web Store webview.
  * @return {Promise} Resolved when the container is ready to be used.
  */
 CWSWidgetContainer.prototype.ready = function() {
   return new Promise(function(resolve, reject) {
     if (this.state_ !== CWSWidgetContainer.State.UNINITIALIZED) {
       reject('Invalid state.');
       return;
     }
 
+    this.spinnerLayerController_.setVisible(true);
+
     this.metricsRecorder_.recordShowDialog();
     this.metricsRecorder_.startLoad();
 
     this.state_ = CWSWidgetContainer.State.GETTING_ACCESS_TOKEN;
 
     this.tokenGetter_.then(function(accessToken) {
       this.state_ = CWSWidgetContainer.State.ACCESS_TOKEN_READY;
       this.accessToken_ = accessToken;
       resolve();
     }.bind(this), function(error) {
+      this.spinnerLayerController_.setVisible(false);
       this.state_ = CWSWidgetContainer.State.UNINITIALIZED;
       reject('Failed to get Web Store access token: ' + error);
     }.bind(this));
   }.bind(this));
 };
 
 /**
  * Initializes and starts loading the Chrome Web Store widget webview.
  * Must not be called before {@code this.ready()} is resolved.
  *
@@ skipping 424 matching lines @@
     function(visible) {
   if (this.visible_ === visible)
     return;
 
   if (this.clearTransition_)
     this.clearTransition_();
 
   this.visible_ = visible;
 
   // Spinner should be shown during transition.
-  if (!this.spinnerLayer_.classList.contains('cws-widget-show-spinner'))
-    this.spinnerLayer_.classList.add('cws-widget-show-spinner');
+  this.spinnerLayer_.classList.toggle('cws-widget-show-spinner', true);
 
   if (this.visible_) {
     this.spinnerLayer_.focus();
    } else if (this.focusOnHide_) {
         this.focusOnHide_.focus();
    }
 
   if (!this.visible_)
     this.spinnerLayer_.classList.add('cws-widget-hiding-spinner');
 
@@ skipping 95 matching lines @@
   this.metricsImpl_.recordUserAction('SuggestApps.ShowDialog');
 };
 
 CWSWidgetContainer.MetricsRecorder.prototype.startLoad = function() {
   this.metricsImpl_.startInterval('SuggestApps.LoadTime');
 };
 
 CWSWidgetContainer.MetricsRecorder.prototype.finishLoad = function() {
   this.metricsImpl_.recordInterval('SuggestApps.LoadTime');
 };