URL: https://codelabs.developers.google.com/
Browser / Version: Firefox 55.0
Operating System: Mac OS X 10.12
Problem type: Text is not visible

Steps to Reproduce

1. Navigate to: https://codelabs.developers.google.com/
2. Wait for the page to fully load (it re-renders itself after bit less than 1 sec)
3. Click the dropdown list 'Category'

Expected Behavior:
It should display a bunch of categories with the text in black and the background in white.

Actual Behavior:
It display a bunch of categories with the text in black and a transparent background making it unreadable.

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