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

if (rootContainerInstance.nodeType === DOCUMENT_NODE) {
      type = '#document';
      let root = (rootContainerInstance: any).documentElement;
      namespace = root ? root.namespaceURI : getChildNamespace(null, '');
    } else {
      const container: any = rootContainerInstance.nodeType === COMMENT_NODE
        ? rootContainerInstance.parentNode
        : rootContainerInstance;
      const ownNamespace = container.namespaceURI || null;
      type = container.tagName;
      namespace = getChildNamespace(ownNamespace, type);
    }
    if (__DEV__) {
      const validatedTag = type.toLowerCase();
      const ancestorInfo = updatedAncestorInfo(null, validatedTag, null);
      return {namespace, ancestorInfo};
    }
    return namespace;
  },
  getChildHostContext(
    parentHostContext: HostContext,
    type: string,