This tests that the ARIA drag and drop attributes work as intended.

PASS: accessibilityController.accessibleElementById('dropeffect-div').ariaDropEffects === 'copy,move'
PASS: initiallyGrabbedDiv.ariaIsGrabbed === true
PASS: initiallyUngrabbedDiv.ariaIsGrabbed === false
PASS: initiallyGrabbedDiv.isAttributeSettable('AXGrabbed') === true
PASS: initiallyUngrabbedDiv.isAttributeSettable('AXGrabbed') === true

Setting aria-grabbed false for element #initially-grabbed-div.
PASS: initiallyGrabbedDiv.ariaIsGrabbed === false

PASS successfullyParsed is true

TEST COMPLETE
drop
grab
grab