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

extensions/browser/guest_view/extension_view/extension_view_guest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/browser/guest_view/extension_view/extension_view_guest.h"
 
 #include "components/crx_file/id_util.h"
 #include "components/guest_view/browser/guest_view_event.h"
 #include "content/public/browser/render_process_host.h"
+#include "content/public/browser/web_contents_source.h"
 #include "content/public/common/result_codes.h"
 #include "extensions/browser/api/extensions_api_client.h"
 #include "extensions/browser/bad_message.h"
 #include "extensions/browser/guest_view/extension_view/extension_view_constants.h"
 #include "extensions/common/constants.h"
 #include "extensions/common/extension_messages.h"
 #include "extensions/strings/grit/extensions_strings.h"
 
 using content::WebContents;
 using guest_view::GuestViewBase;
@@ skipping 64 matching lines @@
     callback.Run(nullptr);
     return;
   }
 
   content::SiteInstance* view_site_instance =
       content::SiteInstance::CreateForURL(browser_context(),
                                           extension_url_);
 
   WebContents::CreateParams params(browser_context(), view_site_instance);
   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 ExtensionViewGuest::DidInitialize(
     const base::DictionaryValue& create_params) {
   ExtensionsAPIClient::Get()->AttachWebContentsHelpers(web_contents());
 
   ApplyAttributes(create_params);
 }
 
 void ExtensionViewGuest::DidAttachToEmbedder() {
@@ skipping 32 matching lines @@
   }
 }
 
 void ExtensionViewGuest::ApplyAttributes(const base::DictionaryValue& params) {
   std::string src;
   params.GetString(extensionview::kAttributeSrc, &src);
   NavigateGuest(src, false /* force_navigation */);
 }
 
 }  // namespace extensions