Implement a basic Site Engagement Score service.

chrome/browser/ui/tab_helpers.cc

Index: chrome/browser/ui/tab_helpers.cc
diff --git a/chrome/browser/ui/tab_helpers.cc b/chrome/browser/ui/tab_helpers.cc
index df974a92d01639e03ee7a7e17d3d48a851ac8d15..fb3a6cefbf0eba0aac86f8c32c437e837af7bc79 100644
--- a/chrome/browser/ui/tab_helpers.cc
+++ b/chrome/browser/ui/tab_helpers.cc
@@ -8,6 +8,8 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/content_settings/chrome_content_settings_client.h"
 #include "chrome/browser/content_settings/tab_specific_content_settings.h"
+#include "chrome/browser/engagement/site_engagement_helper.h"
+#include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/favicon/favicon_helper.h"
 #include "chrome/browser/history/history_tab_helper.h"
 #include "chrome/browser/infobars/infobar_service.h"
@@ -152,6 +154,8 @@ void TabHelpers::AttachTabHelpers(WebContents* web_contents) {
   PrefsTabHelper::CreateForWebContents(web_contents);
   prerender::PrerenderTabHelper::CreateForWebContents(web_contents);
   SearchTabHelper::CreateForWebContents(web_contents);
+  if (SiteEngagementService::IsEnabled())
+    SiteEngagementHelper::CreateForWebContents(web_contents);
   // TODO(vabr): Remove TabSpecificContentSettings from here once their function
   // is taken over by ChromeContentSettingsClient. http://crbug.com/387075
   TabSpecificContentSettings::CreateForWebContents(web_contents);