Tests:
Deleting when a selection starts at the beginning of a text following a nested block, and extends out of the enclosing block into the following block.
FIXME: Currently broken! See rdar://problem/4099839/.
Expected Results:
Should see a total of five lines in the red box, with the third line inside of a nested red box. First line should be "one". Next line should be "two". Next line should be "cha cha cha", inside of a nested red box. Next line should be "ur". The last line should be "cha cha cha". Insertion point should be blinking at the start of the fourth line ("ur").
one
two
cha cha cha
three
four
cha cha cha