Adds the audio history and always on hotwording settings.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index f56543841643a6f0b340a0b28462c54ef382dcff..1b596adcc0ba3541564f1a62ff45be1ed9f749ee 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1788,6 +1788,10 @@ const char kVideoCaptureAllowedUrls[] = "hardware.video_capture_allowed_urls";
 // trigger.
 const char kHotwordSearchEnabled[] = "hotword.search_enabled_2";
 
+// A boolean pref that controls the enabled-state of hotword search voice
+// trigger from any screen.
+const char kHotwordAlwaysOnSearchEnabled[] = "hotword.always_on_search_enabled";
+
 // A boolean pref that controls whether the sound of "Ok, Google" plus a few
 // seconds of audio data before is sent back to improve voice search.
 const char kHotwordAudioLoggingEnabled[] = "hotword.audio_logging_enabled";