Construct the site engagement helper with a site engagement service.

chrome/browser/engagement/site_engagement_helper.h

Index: chrome/browser/engagement/site_engagement_helper.h
diff --git a/chrome/browser/engagement/site_engagement_helper.h b/chrome/browser/engagement/site_engagement_helper.h
index f55ab586b550d7575776d6cbeff02627cb8f50d9..e32632145f251496b5a21f4ba179ac934d55d91c 100644
--- a/chrome/browser/engagement/site_engagement_helper.h
+++ b/chrome/browser/engagement/site_engagement_helper.h
@@ -25,6 +25,8 @@ class SiteEngagementService::Helper
  public:
   ~Helper() override;
 
+  static void CreateForWebContents(content::WebContents* web_contents,
+                                   SiteEngagementService* service);
   static void SetSecondsBetweenUserInputCheck(int seconds);
   static void SetSecondsTrackingDelayAfterNavigation(int seconds);
   static void SetSecondsTrackingDelayAfterShow(int seconds);
@@ -146,7 +148,7 @@ class SiteEngagementService::Helper
     DISALLOW_COPY_AND_ASSIGN(MediaTracker);
   };
 
-  explicit Helper(content::WebContents* web_contents);
+  Helper(content::WebContents* web_contents, SiteEngagementService* service);
   friend class content::WebContentsUserData<SiteEngagementService::Helper>;
   friend class SiteEngagementHelperTest;
 
@@ -165,6 +167,7 @@ class SiteEngagementService::Helper
 
   InputTracker input_tracker_;
   MediaTracker media_tracker_;
+  SiteEngagementService* service_;
   bool record_engagement_;
 
   DISALLOW_COPY_AND_ASSIGN(Helper);