Revert 230235 "Use BaseShellDialog for print dialog on Windows"

Revert 230235 "Use BaseShellDialog for print dialog on Windows"

Per discussion with ananta, opening a system modal dialog from a
background thread is a bad idea, so reverting this (from long ago).
Windows doesn't preserve the order correctly when the window is not on
the main UI thread, and in the bug here, it interacts very badly with
the IME toolbar window, causing the modal print dialog to go behind the
browser window in Z order making chrome appear to be hung.

The original goal was to fix tasks not being dispatched while the dialog
was open. We can instead use the ScopedNestedTaskAllower as we've done
for other system modal dialogs which I'll do in a separate CL.

BUG=342697, 180997
> Use BaseShellDialog for print dialog on Windows
> 
> This puts the print dialog on a background thread which is necessary so other
> top level windows can keep painting as Aura does the compositor swaps on the
> UI thread.
> 
> R=sky@chromium.org,vitalybuka@chromium.org
> 
> 
> Review URL: https://codereview.chromium.org/27441003

TBR=scottmg@chromium.org,sky@chromium.org,vitalybuka@chromium.org,ananta@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251066

[scottmg, 2014-02-13 17:04:34]

Committed patchset #1 manually as r251066.

[Vitaly Buka (NO REVIEWS), 2014-02-13 18:20:41]

lgtm