[MD settings] show icon when slider controlled by something

chrome/browser/resources/settings/a11y_page/manage_a11y_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="../controls/settings_toggle_button.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_shared_css.html">
 <link rel="import" href="../settings_vars_css.html">
 
 <dom-module id="settings-manage-a11y-page">
   <template>
@@ skipping 134 matching lines @@
       </settings-toggle-button>
       <settings-toggle-button
           pref="{{prefs.settings.a11y.large_cursor_enabled}}"
           label="$i18n{largeMouseCursorLabel}">
       </settings-toggle-button>
       <template is="dom-if" if="[[enableAdjustableLargeCursor_]]">
         <div class="list-item">
           <div>$i18n{largeMouseCursorSizeLabel}</div>
           <cr-slider
              disabled="[[!prefs.settings.a11y.large_cursor_enabled.value]]"
-             value="{{prefs.settings.a11y.large_cursor_dip_size.value}}"
+             pref="{{prefs.settings.a11y.large_cursor_dip_size}}"
              min="25" max="64"></cr-slider>
         </div>
       </template>
       <settings-toggle-button
           pref="{{prefs.settings.a11y.cursor_highlight}}"
           label="$i18n{cursorHighlightLabel}">
       </settings-toggle-button>
     </div>
     <div class="settings-box two-line" on-tap="onMouseTap_" actionable>
       <div class="start">
@@ skipping 22 matching lines @@
           $i18n{a11yWebStore}
         </div>
       </div>
       <button class="icon-external" is="paper-icon-button-light"
           aria-label="$i18n{additionalFeaturesTitle}"
           aria-describedby="moreFeaturesSecondary"></button>
     </div>
   </template>
   <script src="manage_a11y_page.js"></script>
 </dom-module>