[MD settings] change dropdown to accept array of objects rather than array of tuples

chrome/browser/resources/settings/appearance_page/appearance_page.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-radio-button/paper-radio-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
+<link rel="import" href="chrome://md-settings/controls/settings_dropdown_menu.html">
 <link rel="import" href="chrome://md-settings/controls/settings_input.html">
 <link rel="import" href="chrome://md-settings/controls/settings_radio_group.html">
 <link rel="import" href="chrome://md-settings/settings_page/settings_animated_pages.html">
 <link rel="import" href="chrome://md-settings/settings_page/settings_subheader.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="appearance_fonts_page.html">
 
 <dom-module id="settings-appearance-page">
   <link rel="import" type="css"
       href="chrome://md-settings/settings_page/settings_page.css">
@@ skipping 60 matching lines @@
           </settings-dropdown-menu>
         </div>
         <div class="settings-box split">
           <div class="start" i18n-content="customizeFonts"></div>
           <paper-button on-tap="onCustomizeFontsTap_"
               i18n-content="customizeFonts"></paper-button>
         </div>
         <div class="settings-box split">
           <div class="start" i18n-content="pageZoom"></div>
           <settings-dropdown-menu id="pageZoom"
-              pref="{{prefs.partition.default_zoom_level}}"
+              pref="{{defaultZoomLevel_}}"
               menu-options="[[pageZoomOptions_]]">
           </settings-dropdown-menu>
         </div>
       </neon-animatable>
       <neon-animatable id="appearance-fonts">
         <settings-subheader i18n-values="page-title:customizeFonts">
         </settings-subheader>
         <template is="dom-if" if="[[showFontsPage_(currentRoute.subpage.*)]]"
             restamp>
           <settings-appearance-fonts-page prefs="{{prefs}}">
           </settings-appearance-fonts-page>
         </template>
       </neon-animatable>
     </settings-animated-pages>
   </template>
   <script src="appearance_page.js"></script>
 </dom-module>