[Hotword] Register audio history pref and use is in chrome://settings.

BUG=426640

Review URL: https://codereview.chromium.org/685963004

Cr-Commit-Position: refs/heads/master@{#302671}

chrome/browser/resources/options/browser_options.html

@@ -196,7 +196,7 @@
         <div id="audio-logging" hidden>
           <div class="checkbox controlled-setting-with-label">
             <label>
-              <input pref="hotword.audio_logging_enabled" type="checkbox">
+              <input pref="hotword.audio_history_enabled" type="checkbox">
               <span i18n-content="hotwordAudioHistoryEnable"></span>
             </label>
           </div>

chrome/browser/search/hotword_service_factory.cc

@@ -111,6 +111,9 @@ void HotwordServiceFactory::RegisterProfilePrefs(
   prefs->RegisterStringPref(prefs::kHotwordPreviousLanguage,
                             std::string(),
                             user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
+  prefs->RegisterBooleanPref(prefs::kHotwordAudioHistoryEnabled,
+                             false,
+                             user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
   // Per-device settings (do not sync).
   prefs->RegisterBooleanPref(prefs::kHotwordSearchEnabled,
                              false,