[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 40bf4b98159d5d6a369ddc165e5b2ad33d7247f2..bc67041abba8713519294d5a3f839f67ad51774e 100644
--- a/chrome/common/url_constants.h
+++ b/chrome/common/url_constants.h
@@ -406,6 +406,9 @@ 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[];