65.0.3286.0 (Official Build) canary (64-bit) (cohort: Clang-64)

Steps to repro:
# Start Chrome
# Visit google.com
# Then visit gmail.com in the same tab
# Press f6 to get to the main toolbar
# Press tab to the 'chrome' menu button
# Press applications key
# Notice nothing happens
# Press down arrow
# Notice the menu opens
# Exit the menu
# Tab to the back button
# Press applications
# Notice the menu opens
# Exit the menu
# Press down arrow
# Notice nothing happens
# Try the same with any extensions on the toolbar
# Try the same with the security chip 
# Notice that, for the security chip, only enter brings up this menu

Expected: Buttons that have submenus should have the same way to activate them. I prefer down arrow

Actual: The user must guess how to activate menus