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

extensions/browser/guest_view/app_view/app_view_guest.cc

Index: extensions/browser/guest_view/app_view/app_view_guest.cc
diff --git a/extensions/browser/guest_view/app_view/app_view_guest.cc b/extensions/browser/guest_view/app_view/app_view_guest.cc
index 64bcd906eee20357c1cd13cbabb722d4130cbe27..78740ccb3a3986de9aa33478e73ebb0fb849c1ea 100644
--- a/extensions/browser/guest_view/app_view/app_view_guest.cc
+++ b/extensions/browser/guest_view/app_view/app_view_guest.cc
@@ -7,6 +7,7 @@
 #include "base/command_line.h"
 #include "components/guest_view/browser/guest_view_manager.h"
 #include "content/public/browser/render_process_host.h"
+#include "content/public/browser/web_contents_source.h"
 #include "content/public/common/renderer_preferences.h"
 #include "extensions/browser/api/app_runtime/app_runtime_api.h"
 #include "extensions/browser/api/extensions_api_client.h"
@@ -249,7 +250,9 @@ void AppViewGuest::CompleteCreateWebContents(
       content::SiteInstance::CreateForURL(browser_context(),
                                           guest_extension->url()));
   params.guest_delegate = this;
-  callback.Run(WebContents::Create(params));
+  WebContents* web_contents = WebContents::Create(params);
+  WebContentsSource::CreateForWebContentsAndLocation(web_contents, FROM_HERE);
+  callback.Run(web_contents);
 }
 
 void AppViewGuest::LaunchAppAndFireEvent(