Chrome Version: (copy from chrome://version)
OS: (e.g. Win10, MacOS 10.12, etc...)

What steps will reproduce the problem?
(1) Browse to a page containing a treeview marked up with ARIA, e.g. https://www.w3.org/TR/2018/WD-wai-aria-practices-1.2-20180719/examples/treeview/treeview-2/treeview-2a.html#tree1
(2) Move ChromeVox focus to a tree item

What is the expected result?

ChromeVox gives guidance on the expected keyboard support (like it does for menus): https://www.w3.org/TR/2018/WD-wai-aria-practices-1.2-20180719/examples/treeview/treeview-2/treeview-2a.html#kbd_label

For example:
"Use right arrow to expand, or up and down arrows to navigate", when collapsed
"Use left arrow to collapse, or up and down arrows to navigate", when expanded

What happens instead?

ChromeVox announces "Press search+space to toggle" - this works, but then the user is lost as there is no guidance on how to explore the tree.