Correct pointer position

Pointer pointed to the right of bubble center. This happened because:
- Bubbles live in expanded view container (x includes expanded view padding)
- Pointer lives in expanded view, which has padding (x does not include padding)

This change removes expanded view padding when deriving pointer location from bubbles.

Bug: 132907741
Test: manual

Change-Id: Ic301d578fee4e6a36be9642ba30ac0cc74cdd3cb