[Hotword] Putting preferences under search for hotword service. Putting behind a flag.

chrome/common/url_constants.h

Index: chrome/common/url_constants.h
diff --git a/chrome/common/url_constants.h b/chrome/common/url_constants.h
index df3c089817f71114e46ffb3a5590c047ea9c0048..56c6e62346eacb54aca35015b32a1837bb7bf7d0 100644
--- a/chrome/common/url_constants.h
+++ b/chrome/common/url_constants.h
@@ -405,6 +405,9 @@ extern const char kBlockedPluginLearnMoreURL[];
 // The URL for the "About Voice Recognition" menu item.
 extern const char kSpeechInputAboutURL[];
 
+// The URL for the "Learn more" page for hotword search voice trigger.
+extern const char kHotwordLearnMoreURL[];
+
 // The URL for the "Learn more" page for register protocol handler infobars.
 extern const char kLearnMoreRegisterProtocolHandlerURL[];