Media Engagement: implement shell of the media engagement 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 a70d9b267a6c77c6f5809e67b6f51e800f5c6fe9..7cb45b44c016e28e61486cc4d13dc426b0198f97 100644
--- a/chrome/browser/ui/tab_helpers.cc
+++ b/chrome/browser/ui/tab_helpers.cc
@@ -22,6 +22,7 @@
 #include "chrome/browser/history/history_tab_helper.h"
 #include "chrome/browser/history/top_sites_factory.h"
 #include "chrome/browser/infobars/infobar_service.h"
+#include "chrome/browser/media/media_engagement_service.h"
 #include "chrome/browser/metrics/desktop_session_duration/desktop_session_duration_observer.h"
 #include "chrome/browser/metrics/renderer_uptime_web_contents_observer.h"
 #include "chrome/browser/net/net_error_tab_helper.h"
@@ -298,4 +299,7 @@ void TabHelpers::AttachTabHelpers(WebContents* web_contents) {
 
   if (tracing::NavigationTracingObserver::IsEnabled())
     tracing::NavigationTracingObserver::CreateForWebContents(web_contents);
+
+  if (MediaEngagementService::IsEnabled())
+    MediaEngagementService::CreateWebContentsObserver(web_contents);
 }