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See my earlier reply on May 2 (and giving proper credit to @Brandi Stewart for the original answer):
"pressing that nasty top control bar" or "moving your mouse to make it appear" is not entirely complete; press somewhere on the top control bar to make it 'active' -- i found pressing the time clock on the Sharing Toolbar to be the most innocuous part to click to make it 'active'.
Then the Ctrl-W (Cmd-W on Macs) makes it disappear -- and I don't think there's a way to make the control-bar reappear -- all I've found is to Stop Sharing, and then resume Sharing to have it go back to the default of appearing when you mouse up to the top -- and it's hiding your browser tabs again :-| )