Google Chrome	71.0.3558.0 (Official Build) dev (64-bit)
Firmware Version	Google_Caroline.7820.384.0

Steps to reproduce:
# Download a .docx, .xlsx, or .pptx file (I created these by using "Download as" from Google Docs/Sheets/Slides)
# Open it locally in Chrome OS out of files, opening the Office Editing extension 
# Press ctrl + / to open keyboard shortcuts
# Use arrow keys to attempt to scroll up and down the list
Expected: able to scroll the list 
Actual: unable to scroll the list using keyboard only