See https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=132771

Steps to Reproduce:
1. Open two windows on the screen
2. Position window A so its upper-left corner is near the center of
the screen, with space above it to accomodate window B's entire height
3. Hold down Shift and position window B so its lower-left corner
rests on window A's upper-left corner
4. Continuing to hold down Shift, move window B straight up

Actual Results:  Window B temporarily jumps straight up, locking on to
the top edge of the screen (so its left edge remains aligned with
window A's left edge), then quickly jumps to one of the corners (as if
it "lost" its lock with the left edge of window A).

Expected Results:  Either moving window A up should cause it to
immediately jump into a locked position in the screen corner, or it
should remain "locked" against the left edge of window B (that it was
just previously locked against) against the top edge of the screen.
None of this jumping up, then a split second later jumping over.