[TIMOB-15304] Accessibility Voice Over is Blocked by higher windows

When a smaller window is opened over a fullscreen window, the smaller window blocks entirely the accessibility voiceover of the lower window. The smaller window should only cover the area that it physically covers, not the entire screen. I have included an app.js that shows this issue. 1. Start the app w/ Accessibility Controls enabled 2. Click the button and note that it is found by the accessibility system 3. Double click (to actually click the button) and a smaller window is opened across the bottom (in red). 4. Clicking on the red gives you accessibility info about the red area, but the button is not not accessible. It is hidden entirely by the higher window. REGRESSION: This is a regression from (roughly) 3.0 when the accessibility area was restricted to the area of the window, and the button would also have accessibility information available to the accessibility system.