Test case for fix for http://bugzilla.opendarwin.org/show_bug.cgi?id=5354.

Changes were made to VisiblePosition's so that init() will not leave the block containing the requested position unless there are no VisiblePositions in that block.

Select All while inside this editable block should create a selection that does not extend outside of this block.

This is a paragraph outside the editable block with overflow:hidden