MD Settings: add tests for mischievous default zoom handling

chrome/browser/resources/settings/appearance_page/appearance_page.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.
 
 /**
  * 'settings-appearance-page' is the settings page containing appearance
  * settings.
  *
  * Example:
  *
@@ skipping 13 matching lines @@
      * Dictionary defining page visibility.
      * @type {!AppearancePageVisibility}
      */
     pageVisibility: Object,
 
     prefs: {
       type: Object,
       notify: true,
     },
 
-    /** @private {!settings.AppearanceBrowserProxy} */
-    browserProxy_: Object,
-
     /** @private */
     defaultZoom_: Number,
 
     /**
      * List of options for the font size drop-down menu.
      * @type {!DropdownMenuOptionList}
      */
     fontSizeOptions_: {
       readOnly: true,
       type: Array,
@@ skipping 40 matching lines @@
     /** @private */
     themeSublabel_: String,
 
     /** @private */
     useSystemTheme_: {
       type: Boolean,
       value: false,  // Can only be true on Linux, but value exists everywhere.
     },
   },
 
+  /** @private {?settings.AppearanceBrowserProxy} */
+  browserProxy_: null,
+
   /** @private {string} */
   themeUrl_: '',
 
   observers: [
     'themeChanged_(prefs.extensions.theme.id.value, useSystemTheme_)',
 
 <if expr="is_linux and not chromeos">
     // NOTE: this pref only exists on Linux.
     'useSystemThemePrefChanged_(prefs.extensions.theme.use_system.value)',
 </if>
   ],
 
   created: function() {
     this.browserProxy_ = settings.AppearanceBrowserProxyImpl.getInstance();
   },
 
   ready: function() {
     this.$.defaultFontSize.menuOptions = this.fontSizeOptions_;
     // TODO(dschuyler): Look into adding a listener for the
     // default zoom percent.
-    chrome.settingsPrivate.getDefaultZoom(function(zoom) {
+    this.browserProxy_.getDefaultZoom().then(function(zoom) {
       this.defaultZoom_ = zoom;
     }.bind(this));
   },
 
   /**
    * @param {number} zoom
    * @return {number} A zoom easier read by users.
    * @private
    */
   formatZoom_: function(zoom) {
@@ skipping 130 matching lines @@
    * @see content::ZoomValuesEqual().
    * @param {number} zoom1
    * @param {number} zoom2
    * @return {boolean}
    * @private
    */
   zoomValuesEqual_: function(zoom1, zoom2) {
     return Math.abs(zoom1 - zoom2) <= 0.001;
   },
 });