This is not the same question as ES6 Modules In Google Chrome Extension Development (unexpected token) as that is both outdated and already answered.
Google produced a n
As user wOxxOm mentioned in comments, see https://crbug.com/738739.
9-18-17 update: https://bugs.chromium.org/p/chromium/issues/detail?id=769012 looks like it is being fixed!
10-19-17 update: https://bugs.chromium.org/p/chromium/issues/detail?id=728377#c18 reported as working in chrome 64 (currently canary)
11-13-17 update: final update, testing in Chrome 63, modules are now working. Note that if you need to load a module in the background page of the extension, you cannot do it via scripts property in manifest.json, instead set page to background.html, and specify type module in script tag, and that will bypass the manifest issue.