electron: Devtool extensions don't show up on first load

• Electron version: 1.2.2+
• Operating system: Windows

React Developer Tools work’s as expected in 1.2.1 but any version above that reports a successful install but the Dev Tools do not appear.

I have tried both file:// URL’s and http:// URL’s, neither trigger the React DevTools. This is because the __REACT_DEVTOOLS_GLOBAL_HOOK__ global variable is never set. Possibly an issue with running content scripts?