Chrome: 64.0.3273.3 (Official Build) canary (64-bit) (cohort: Clang-64)
Firefox: 52.4.1 (64-bit)
Jaws: 2018
NVDA: 2017.3

Steps to repro: Tested in Chrome and Firefox
# With NVDA running, In Chrome: Visit https://www.google.com/chrome/browser/desktop/index.html?brand=CHBD
# Click download
# Press alt+d to jump to the omnibox
# Press tab multiple times and observe where the focus is
# Notice that we have escaped the modal and are tabbing behind the modal
# Notice that NVDA says 'blank' 

Expected: When focus escapes the modal, it should be brought back to the first focusable element in the modal.

Actual: Focus is allowed to remain behind the modal.

# Press down arrow several times
# Notice that NVDA says blank
# Notice that it is nearly impossible to focus the dialog with tab or arrows

Expected: NVDA should be able to find the modal with arrows and bring focus back to the modal.

Actual: It seems to be stuck in aria-hidden content

# With JAWS running, In Chrome: Visit https://www.google.com/chrome/browser/desktop/index.html?brand=CHBD
# Click download
# Press alt+d to jump to the omnibox
# Press tab multiple times and observe where the focus is
# Notice that we have escaped the modal and are tabbing behind the modal
# Notice that JAWS says 'Google Chrome'

Expected: When focus escapes the modal, it should be brought back to the first focusable element in the modal.

Actual: Focus is allowed to remain behind the modal.

# Press down arrow several times
# Notice that JAWS begins to read modal content
# Notice that after JAWS encounters a focusable element, focus is brought to the modal

Expected: JAWS and NVDA should be able to recover and focus the modal again

Actual: Only JAWS recovers properly.