Web worker and "undefined" warnings in repo_edit_button_spec.js
```
RepoEditButton
✔ renders an edit button
✔ renders edit button with cancel text
✔ toggles edit mode on click
discardPopupOpen
✔ renders popup
✔ removes all changed files
19 02 2018 18:53:05.297:WARN [web-server]: 404: /assets/webpack/monaco-editor/vs/base/worker/workerMain.js
WARN: 'Could not create web worker(s). Falling back to loading web worker code in main thread, which might cause UI freezes. Please see https://github.com/Microsoft/monaco-editor#faq'
WARN: 'Could not create web worker(s). Falling back to loading web worker code in main thread, which might cause UI freezes. Please see https://github.com/Microsoft/monaco-editor#faq'
WARN: undefined
WARN: undefined
WARN: undefined
WARN: undefined
RepoEditor
✔ renders an ide container
19 02 2018 18:53:05.349:WARN [web-server]: 404: /assets/webpack/monaco-editor/vs/base/worker/workerMain.js
WARN: undefined
WARN: undefined
WARN: undefined
WARN: undefined
when open file is binary and not raw
✔ does not render the IDE
19 02 2018 18:53:05.377:WARN [web-server]: 404: /assets/webpack/monaco-editor/vs/base/worker/workerMain.js
WARN: undefined
WARN: undefined
WARN: undefined
WARN: undefined
✔ shows activeFile html
```
(https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/53309451)
issue