Track where WebContents are created in order to better understand issue.

components/guest_view/browser/guest_view_manager.cc

Index: components/guest_view/browser/guest_view_manager.cc
diff --git a/components/guest_view/browser/guest_view_manager.cc b/components/guest_view/browser/guest_view_manager.cc
index 4c86e9d17439fad976ee75dc623b66492bfc72bc..5bb9fa55b3294ee1095c98c2f221c540d394eae3 100644
--- a/components/guest_view/browser/guest_view_manager.cc
+++ b/components/guest_view/browser/guest_view_manager.cc
@@ -16,6 +16,7 @@
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/user_metrics.h"
 #include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_source.h"
 #include "content/public/common/child_process_host.h"
 #include "content/public/common/result_codes.h"
 #include "content/public/common/url_constants.h"
@@ -180,6 +181,8 @@ content::WebContents* GuestViewManager::CreateGuestWithWebContentsParams(
   content::WebContents::CreateParams guest_create_params(create_params);
   guest_create_params.guest_delegate = guest;
   auto guest_web_contents = WebContents::Create(guest_create_params);
+  WebContentsSource::CreateForWebContentsAndLocation(guest_web_contents,
+                                                     FROM_HERE);
   guest->InitWithWebContents(base::DictionaryValue(), guest_web_contents);
   return guest_web_contents;
 }