Google Chrome 66.0.3349.0 (Official Build) canary (64-bit) (cohort: 64-Bit) 
Google Chrome 64.0.3282.167 (Official Build) (64-bit) (cohort: Stable)
macOS Sierra 10.12.6
Full Keyboard access enabled on Mac to allow tab to move focus between all controls	

Steps to repro:
# Launch Add bookmark dialog (press star or ctrl + d)
# Navigate around the folders where you could save your bookmarks using the arrow keys
Expected behavior: pressing down arrow on the last folder in the list either does nothing or wraps to the top of the folder list (unclear which is expected)
Actual: pressing down arrow on the last folder in the folder list will break out of the list and bring you to the edit menu.