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

extensions/browser/extension_host.cc

Index: extensions/browser/extension_host.cc
diff --git a/extensions/browser/extension_host.cc b/extensions/browser/extension_host.cc
index df7b74d754d6df61fb5ed111b2bb64b6f7140bee..eb2a0cf4ba245ae1716d69675c1f075a152cf0a2 100644
--- a/extensions/browser/extension_host.cc
+++ b/extensions/browser/extension_host.cc
@@ -19,6 +19,7 @@
 #include "content/public/browser/render_widget_host_view.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/bad_message.h"
 #include "extensions/browser/event_router.h"
 #include "extensions/browser/extension_error.h"
@@ -70,7 +71,9 @@ ExtensionHost::ExtensionHost(const Extension* extension,
          host_type == VIEW_TYPE_EXTENSION_DIALOG ||
          host_type == VIEW_TYPE_EXTENSION_POPUP);
   host_contents_.reset(WebContents::Create(
-      WebContents::CreateParams(browser_context_, site_instance))),
+      WebContents::CreateParams(browser_context_, site_instance)));
+  WebContentsSource::CreateForWebContentsAndLocation(host_contents_.get(),
+                                                     FROM_HERE);
   content::WebContentsObserver::Observe(host_contents_.get());
   host_contents_->SetDelegate(this);
   SetViewType(host_contents_.get(), host_type);