Adding previews information to PLM UKM

chrome/browser/previews/previews_infobar_tab_helper.h

Index: chrome/browser/previews/previews_infobar_tab_helper.h
diff --git a/chrome/browser/previews/previews_infobar_tab_helper.h b/chrome/browser/previews/previews_infobar_tab_helper.h
index 949ac7ea2f1ca34720c005d7ba8d9b2c7d3d9142..ec496573beb8549e29604367c4009191d268371a 100644
--- a/chrome/browser/previews/previews_infobar_tab_helper.h
+++ b/chrome/browser/previews/previews_infobar_tab_helper.h
@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "base/optional.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_pingback_client.h"
+#include "components/ukm/ukm_source.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
@@ -37,6 +38,9 @@ class PreviewsInfoBarTabHelper
     return committed_data_saver_navigation_id_;
   }
 
+  // Source ID for the last main frame navigation.
+  base::Optional<ukm::SourceId> source_id() const { return source_id_; }
+
  private:
   friend class content::WebContentsUserData<PreviewsInfoBarTabHelper>;
   friend class PreviewsInfoBarTabHelperUnitTest;
@@ -60,6 +64,9 @@ class PreviewsInfoBarTabHelper
   base::Optional<data_reduction_proxy::NavigationID>
       committed_data_saver_navigation_id_;
 
+  // Source ID for the last main frame navigation.
+  base::Optional<ukm::SourceId> source_id_;
+
   DISALLOW_COPY_AND_ASSIGN(PreviewsInfoBarTabHelper);
 };