Support braille commands in ChromeVox Next.
This includes commands inside of views and web contents. The distinction no longer matters because of the automation tree. It also works in the various modes utilizing the automation tree (Next, force next, and compat). This enables panning inside of the shelf for the first time in ChromeVox since compat mode is now enabled by default there.
TEST=command inside of OOBE, shelf.
BUG=488693
Review URL: https://codereview.chromium.org/
1218103003
Cr-Commit-Position: refs/heads/master@{#338867}