mouseMoveAt() confused by scroll on outer document

[bill]

On IE8 I get dueling scrollbars on the test_ComboBox test:

1. scrollbar on the <iframe> loading tests/form/_autoComplete.html
2. scrollbar on the browser window

When the robot test focuses on a ComboBox towards the bottom of the page, IE makes the ComboBox visible by scrolling one or both of those <div>'s. (This is happening as I call myCombo.focusNode.focus(), so dijit.scrollIntoView() is not in play here.

At this point doh.robot.mouseMoveOver() stops working correctly as it isn't taking scrollOffset into account.

See attached test file (simplified version of ComboBox? test.)

[Douglas Hays]

dup of #8957