[Hotword] Add error message display back in. Add error messages for NaCl. Add metrics for errors.

chrome/browser/resources/options/content_settings.html

 <div id="content-settings-page" class="page" hidden>
   <div class="close-button"></div>
   <h1 i18n-content="contentSettingsPage"></h1>
   <div class="content-area">
     <!-- Cookie filter tab contents -->
     <section>
       <h3 i18n-content="cookies_tab_label"></h3>
       <div>
         <div class="radio">
           <span class="controlled-setting-with-label">
@@ skipping 404 matching lines @@
         <div class="settings-row">
           <button id="protected-content-exceptions"
               class="exceptions-list-button" contentType="protectedContent"
               i18n-content="manageExceptions"></button>
         </div>
   </if>
       </div>
     </section>
 </if>
     <!-- Media Stream capture device filter -->
-    <section>
+    <section id="media-stream-settings">
       <div class="section-header">
         <h3 i18n-content="mediaStreamTabLabel"></h3>
         <span id="media-indicator"
             class="controlled-setting-indicator group-indicator"></span>
       </div>
       <div>
         <div class="media-device-control">
           <span i18n-content="mediaSelectMicLabel"></span>
           <select id="media-select-mic" class="weakrtl"></select>
         </div>
@@ skipping 161 matching lines @@
     </section>
   </div>
   <div class="action-area">
     <div class="button-strip">
       <button id="content-settings-overlay-confirm" class="default-button"
           i18n-content="done">
       </button>
     </div>
   </div>
 </div>