Add desktop engagement metrics.

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 85c3e1d5118b996cde98f1f0002cd640c582e82a..75e3d45b41561c76c9c8197635bb10f6a7d2b12b 100644
--- a/chrome/browser/ui/tab_helpers.cc
+++ b/chrome/browser/ui/tab_helpers.cc
@@ -16,6 +16,7 @@
 #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/metrics/desktop_engagement/desktop_engagement_observer.h"
 #include "chrome/browser/net/net_error_tab_helper.h"
 #include "chrome/browser/net/predictor_tab_helper.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_initialize.h"
@@ -218,6 +219,10 @@ void TabHelpers::AttachTabHelpers(WebContents* web_contents) {
     banners::AppBannerManagerDesktop::CreateForWebContents(web_contents);
 #endif
 
+#if defined(OS_WIN) || defined(OS_MACOSX) || \
+    (defined(OS_LINUX) && !defined(OS_CHROMEOS))
+    metrics::DesktopEngagementObserver::CreateForWebContents(web_contents);
+#endif
   // --- Feature tab helpers behind flags ---
 
 #if defined(ENABLE_CAPTIVE_PORTAL_DETECTION)