popups/dnd placement off by a scrollbar width in themeTester

[peller]

[11944] caused UT failure in IE6/7. Had to back out this line in _base/html.js

+			return scrollLeft + de.clientWidth - de.scrollWidth; // Integer
-			return de.clientWidth - de.offsetWidth; // Integer

Now the unit tests pass again, but we're off by a scrollbar width.

[peller]

(In [11955]) Fixes bidi in quirks mode (thanks, makin) Fixes #3721 and backs out change from [11944] Refs #5509. Plus some size reductions. !strict

[peller]

must have something to do with the fact that there's a scrollbar on a pane that's not the main document.