UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/64.0.3282.167 Chrome/64.0.3282.167 Safari/537.36

Steps to reproduce the problem:
In a Chrome extension (or the dev tools console for an existing running Chrome extension), attempt to send a message to the U2F extension:

chrome.runtime.sendMessage('kmendfapggjehodndflmmgagdbamhnfd', {
        type: 'u2f_sign_request',
        signRequests: []
  }, function() {
  if (!chrome.runtime.lastError) {
    // We are on a whitelisted origin and can talk directly
    // with the extension.
    console.log('Success')
  } else {
    // chrome.runtime was available, but we couldn't message
    // the extension directly, use iframe
    console.log(chrome.runtime.lastError)
  }
});

What is the expected behavior?
"Success" is logged to the console, as it would be if this code were run by a web page.

What went wrong?
'{message: "Could not establish connection. Receiving end does not exist."}' is logged to the console, indicating that it was not possible to send the message.

Did this work before? No 

Does this work in other browsers? Yes

Chrome version: 64.0.3282.167  Channel: stable
OS Version: Ubuntu 16.04
Flash Version: 

The iframe trampoline technique described in https://github.com/google/u2f-ref-code/blob/master/u2f-chrome-extension/README.md also doesn't work.