Revert of Allows menu host windows to be enumerated in DragTargetWindowFinder

Revert of Allows menu host windows to be enumerated in DragTargetWindowFinder (https://codereview.chromium.org/196213004/)

Reason for revert:
Seems to have broken views_unittests on the Linux builder.

Original issue's description:
> Allows menu host windows to be enumerated in DragTargetWindowFinder.
> We create a cache that holds all XIDs of the menu windows that get created in X. The menus are evaluated for being drop targets before enumerating other windows. The menu XIDs cache gets updated in a root X11DesktopHandler when any menu (and Chrome menu in particular) gets created.
> 
> TBR(sky) for OWNERS in ui/base/ui_base.gyp.
> 
> BUG=349154, 349156, 344747
> TBR=sky
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=260046

TBR=sadrul@chromium.org,erg@chromium.org,varkha@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=349154, 349156, 344747
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=260062

[calamity, 2014-03-28 02:28:29]

Created Revert of Allows menu host windows to be enumerated in
DragTargetWindowFinder

[commit-bot: I haz the power, 2014-03-28 02:29:53]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/calamity@chromium.org/216133002/1

[commit-bot: I haz the power, 2014-03-28 02:31:51]

Change committed as 260062