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

extensions/browser/app_window/app_window_contents.cc

Index: extensions/browser/app_window/app_window_contents.cc
diff --git a/extensions/browser/app_window/app_window_contents.cc b/extensions/browser/app_window/app_window_contents.cc
index 03629988e967409ab66c987eee21555072a5ffbb..06bdd8d1e13d04e91377e05643bf4415f42680fa 100644
--- a/extensions/browser/app_window/app_window_contents.cc
+++ b/extensions/browser/app_window/app_window_contents.cc
@@ -15,6 +15,7 @@
 #include "content/public/browser/resource_dispatcher_host.h"
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_source.h"
 #include "content/public/common/renderer_preferences.h"
 #include "extensions/browser/app_window/native_app_window.h"
 #include "extensions/common/extension_messages.h"
@@ -33,6 +34,8 @@ void AppWindowContentsImpl::Initialize(content::BrowserContext* context,
   web_contents_.reset(
       content::WebContents::Create(content::WebContents::CreateParams(
           context, content::SiteInstance::CreateForURL(context, url_))));
+  WebContentsSource::CreateForWebContentsAndLocation(web_contents_.get(),
+                                                     FROM_HERE);
 
   Observe(web_contents_.get());
   web_contents_->GetMutableRendererPrefs()->