No testdriver.js method for sequential navigation

[hugoholgersson]

To be able to test sequential navigation (and also spatial navigation) in WPT, we need a testdriver.js method for moving focus: forward, backward (and also up, down, left, right).

We cannot use test_driver.send_keys() because:

1. Browsers might use different key-mappings even though typically tab-key is used.
2. send_keys() might do unwanted scrolling.
3. We do not want to target a specific element.

We simply want the browser to move focus in whatever browser-dependent way it likes (and resolve a promise once it has done so).

As of now, Chrome's sequential and spatial navigation tests must use eventSender. This blocks us from upstreaming these tests to WPT.

I suspect we need underlaying WebDriver support to do be able to test this across browsers.

[foolip]

My strawman API would be test_driver.focus_next() and test_driver.focus_previous() methods. Under the hood it might send tab characters in some implementations, so it this should also be documented, so that tests don't react to those events and break. To maintain the possibility of not using tab keys to trigger this, it would actually be good if some browsers didn't. Probably accessibility APIs can also be used to cycle focus.

[mdittmer]

Friendly ecosystem infra rotation ping

If this is priority:roadmap should it have an assignee?

[foolip]

@LukeZielinski do you have a prioritized list of missing capabilities? Does this make the cut for what we should fix soon?

[foolip]

I'll go ahead and decrease the priority of this until there are more people asking for it.

[domenic]

Note that @rakina wrote up a pull request here which assumes TAB key. https://github.com/web-platform-tests/wpt/pull/17523/files#diff-6d8e45f94b9f120a854ec188b4857275R67

If we believe that's not the correct approach then fixing this seems relatively high priority.