Fix focus bug with shell dialogs

The focus is not restored properly when a Windows modal dialog
(such as "open file', 'print'...) is closed.
We are running these dialogs from a different thread and they
cause the browser window to get activated before it has been
enabled. This causes the focus restoration to fail as the window
is not enabled.
In an earlier patch, I fixed it by storing/restoring the focus
explicitly before/after the dialog is shown.
But the fix did not apply to the print dialog which does not use
the code I added my fix in.

This CL reverts that previous fix and comes with a simpler solution:
if when we are about to restore focus the window is disabled, we
delay the focus restoration untill the window is enabled again.

BUG=3380
TEST=Set the focus on a page with scroll-bars, right-click to do a
    'save as'. Close the dialog. The arrow keys should let you scroll
    the page. Accelerators such as Ctrl-T should still work. Test
    'open a file', 'print' and the font selection dialog (in the options).
    When closing the dialog the focus should return to the view that last
    had focus. 


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=26135

[ananta, 2009-09-14 18:52:00]

LGTM