Checking again with flag disabled: 

70.0.3524.2 (Official Build) canary (64-bit)
Google_Eve.9584.160.0
#ash-keyboard-shortcut-viewer-app set to 'Disabled' 

Does not reproduce using above steps; closing as WontFix.

Actually, reopening since I'll let the team decide whether or not to close this bug based on the above finding. 

I thought I had this working...

To clarify, with the flag set to enabled, I am only able to linear navigate across the entire window, minimize, and close buttons. I am not able to linear navigate into the shortcuts themselves. 

Repro is a little tricky.

This works OK:
* Turn off ChromeVox
* Restart Chrome
* Open shortcut viewer
* Turn on ChromeVox
Highlight moves to search field and you can linear navigate.

This does not work:
* Turn off ChromeVox
* Restart Chrome
* Turn on ChromeVox
* Turn off ChromeVox
* Open shortcut viewer
* Turn on ChromeVox again
Now you can't linear navigate.

There's something special about having turned ChromeVox on and off before. Digging more...

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f843782205ad1bb097af41faa352e2ffa23fe216

commit f843782205ad1bb097af41faa352e2ffa23fe216
Author: James Cook <jamescook@chromium.org>
Date: Thu Aug 23 17:34:56 2018

chromeos: Fix turning on ChromeVox after shortcut viewer app is open

If ChromeVox has ever been turned on during a user session then
AutomationManagerAura and AXHostService will be enabled, even if
ChromeVox is turned off later. When the shortcut viewer app launches
it sees automation is enabled and AXRemoteHost caches the enabled state.

When ChromeVox is turned on again AXHostService will generate another
OnAutomationEnabled() message to the remote app. Instead of just
early-exiting because "automation is already on", re-serialize the
app's node tree and send load complete.

This is consistent with how AutomationManagerAura behaves today.

Bug:  876407 
Test: added to views_mus_unittests
Change-Id: Ib906da907ca20bbaa3509af72b137462ba006e28
Reviewed-on: https://chromium-review.googlesource.com/1185897
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585533}
[modify] https://crrev.com/f843782205ad1bb097af41faa352e2ffa23fe216/ui/views/mus/ax_remote_host.cc
[modify] https://crrev.com/f843782205ad1bb097af41faa352e2ffa23fe216/ui/views/mus/ax_remote_host_unittest.cc