Merge 33287 - Mac: improve apparent zorder problems when switching Spaces....

Merge 33287 - Mac: improve apparent zorder problems when switching Spaces.

Remove the status bubble as child window when hidden, rather than just setting
its opacity to 0. I'm not sure about the effects, if any, of doing this rather
than destroying the window completely. This doesn't eliminate zorder problems
with Spaces, but should improve it considerably.

This may also ameliorate the problems with moving windows between Spaces using
Expose.

BUG=28107, 24956
TEST=Create a bunch of windows; get the status bubble to appear in the active (key) window and then get it to disappear; switch to another spaces and back; make sure the active window is on top; repeat.

Review URL: http://codereview.chromium.org/434120

TBR=pinkerton@chromium.org, thakis@chromium.org, viettrungluu@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=33297