This is a bug report.

**Expected Behavior**
React should not suggest me to download the DevTools extension in a `chrome-extension://` page, because the extension has no permission to inject the devtool.

**Actual Behavior**
`Download the React DevTools and use an HTTP server (instead of a file: URL) for a better development experience: https://fb.me/react-devtools`

**Reproducing**

1. Create a Chrome extension with an `option` or `popup` page that uses React
2. Load the extension to Chrome and open up that page.
3. Observe console.

**Version**
Google Chrome 56.0.2924.3
React 15.4.0

| (Element & {
    _reactRootContainer: ?Object,
  })
  | (Document & {
    _reactRootContainer: ?Object,
  });
type Container = Element | Document;
type Props = {
  autoFocus?: boolean,
  children?: mixed,
  hidden?: boolean,
};
type Instance = Element;
type TextInstance = Text;
type HostContextDev = {
  namespace: string,
  ancestorInfo: mixed,
};
type HostContextProd = string;
type HostContext = HostContextDev | HostContextProd;
let eventsEnabled: ?boolean = null;
let selectionInformation: ?mixed = null;
/**
 * True if the supplied DOM node is a valid node element.
 *
 * @param {?DOMElement} node The candidate DOM node.
 * @return {boolean} True if the DOM is a valid DOM node.
 * @internal
 */
function isValidContainer(node) {