This implements WebDriver Actions API support for key sequences with
modifier tracking in our testdriver-vendor.js. The action_sequence
function processes key sources, tracks Shift/Ctrl/Alt/Meta state across
events, and dispatches keys with the appropriate modifiers via
Internals.sendText().
This allows us to pass WPT tests that make use of that API in our own
test-web runner.
This change imports the WPT accname/name/comp_embedded_control.html
test, along with related resources files it depends on.
Note that in the wai-aria/scripts/aria-utils.js file, this changes the
get_computed_label call to use our window.internals.getComputedLabel.