MD Settings: [further] robustify default zoom level 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 94 matching lines @@
 
   created: function() {
     this.browserProxy_ = settings.AppearanceBrowserProxyImpl.getInstance();
   },
 
   ready: function() {
     this.$.defaultFontSize.menuOptions = this.fontSizeOptions_;
     // TODO(dschuyler): Look into adding a listener for the
     // default zoom percent.
     chrome.settingsPrivate.getDefaultZoom(function(zoom) {
-      this.$.zoomLevel.value = zoom;
+      assert(this.pageZoomLevels_.length == this.$.zoomLevel.options.length);
+      for (var i = 0; i < this.pageZoomLevels_.length; ++i) {

[dpapad, 2016/11/10 00:30:58]

If we have to iterate over zoom levels, would it make sense to add a binding
instead?

 <option value="[[item]]"
selected$="[[isSelected_(item,zoomLevel)]]">[[formatZoom_(item)]]%</option>

properties: {
 ...
 zoomLevel: Number
}

isSelected_: function(item) {
  return Math.abs(item - this.zoomLevel) <= 0.001;
}

[Dan Beam, 2016/11/10 01:22:11]

Done.

+        // See content::ZoomValuesEqual().
+        if (Math.abs(this.pageZoomLevels_[i] - zoom) <= 0.001) {
+          this.$.zoomLevel.selectedIndex = i;
+          return;
+        }
+      }
+      assertNotReached();
     }.bind(this));
   },
 
   /**
    * @param {number} zoom
    * @return {number} A zoom easier read by users.
    * @private
    */
   formatZoom_: function(zoom) {
     return Math.round(zoom * 100);
@@ skipping 118 matching lines @@
 
   /**
    * @param {boolean} bookmarksBarVisible if bookmarks bar option is visible.
    * @return {string} 'first' if the argument is false or empty otherwise.
    * @private
    */
   getFirst_: function(bookmarksBarVisible) {
     return !bookmarksBarVisible ? 'first' : '';
   }
 });