chrome/browser/resources/settings/site_favicon.js

// Copyright 2018 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.

/**
 * @fileoverview 'site-favicon' is the section to display the favicon given the
 * site URL.
 */

Polymer({
  is: 'site-favicon',

  properties: {
    url: {
      type: String,
      value: '',
      observer: 'urlChanged_',
    }
  },

  /** @private */
  urlChanged_: function() {
    let url = this.removePatternWildcard_(this.url);
    url = this.ensureUrlHasScheme_(url);
    this.style.backgroundImage = cr.icon.getFavicon(url || '');
  },

  /**
   * Removes the wildcard prefix from a pattern string.
   * @param {string} pattern The pattern to remove the wildcard from.
   * @return {string} The resulting pattern.
   * @private
   */
  removePatternWildcard_: function(pattern) {
    if (!pattern || pattern.length === 0)
      return pattern;

    if (pattern.startsWith('http://[*.]'))
      return pattern.replace('http://[*.]', 'http://');
    else if (pattern.startsWith('https://[*.]'))
      return pattern.replace('https://[*.]', 'https://');
    else if (pattern.startsWith('[*.]'))
      return pattern.substring(4, pattern.length);
    return pattern;
  },

  /**
   * Ensures the URL has a scheme (assumes http if omitted).
   * @param {string} url The URL with or without a scheme.
   * @return {string} The URL with a scheme, or an empty string.
   * @private
   */
  ensureUrlHasScheme_: function(url) {
    if (!url || url.length === 0)
      return url;
    return url.includes('://') ? url : 'http://' + url;
  },
});