WebUI: Polymer config tweaks for better performance.

chrome/browser/resources/settings/privacy_page/privacy_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_dialog/cr_dialog.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_vars_css.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout-classes.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-icon-button/paper-icon-button-light.html">
 <link rel="import" href="../clear_browsing_data_dialog/clear_browsing_data_dialog.html">
@@ skipping 93 matching lines @@
                   class="more-actions">
                 $i18n{restart}
               </paper-button>
             </template>
           </settings-toggle-button>
         </div>
 </if><!-- not chromeos -->
 </if><!-- _google_chrome -->
         <div class="settings-box">
           <template id="doNotTrackDialogIf" is="dom-if"
-              if="[[showDoNotTrackDialog_]]">
+              if="[[showDoNotTrackDialog_]]" notify-dom-change>

[Dan Beam, 2017/03/15 19:49:31]

stevenjb

             <dialog is="cr-dialog" id="confirmDoNotTrackDialog"
                 close-text="$i18n{close}" on-cancel="onDoNotTrackDialogCancel_">
               <div class="title">$i18n{doNotTrackDialogTitle}</div>
               <div class="body">$i18nRaw{doNotTrackDialogMessage}</div>
               <div class="button-container">
                 <paper-button class="cancel-button"
                     on-tap="onDoNotTrackDialogCancel_">
                   $i18n{cancel}
                 </paper-button>
                 <paper-button class="action-button"
@@ skipping 348 matching lines @@
                 category="{{ContentSettingsTypes.PROTECTED_CONTENT}}">
             </category-setting-exceptions>
           </template>
 </if>
         </settings-subpage>
       </template>
     </settings-animated-pages>
   </template>
   <script src="privacy_page.js"></script>
 </dom-module>