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

chrome/browser/background/background_contents.cc

Index: chrome/browser/background/background_contents.cc
diff --git a/chrome/browser/background/background_contents.cc b/chrome/browser/background/background_contents.cc
index 20190fd4218d3632c6ecd700e50ad20d45d5e306..cfd2161567fbf4e001ee06ce7730be87352ab2f2 100644
--- a/chrome/browser/background/background_contents.cc
+++ b/chrome/browser/background/background_contents.cc
@@ -18,6 +18,7 @@
 #include "content/public/browser/session_storage_namespace.h"
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_source.h"
 #include "extensions/browser/deferred_start_render_host_observer.h"
 #include "extensions/browser/extension_host_delegate.h"
 #include "extensions/browser/extension_host_queue.h"
@@ -55,6 +56,8 @@ BackgroundContents::BackgroundContents(
         create_params, session_storage_namespace_map));
   } else {
     web_contents_.reset(WebContents::Create(create_params));
+    WebContentsSource::CreateForWebContentsAndLocation(web_contents_.get(),
+                                                       FROM_HERE);
   }
   extensions::SetViewType(
       web_contents_.get(), extensions::VIEW_TYPE_BACKGROUND_CONTENTS);