Make sure bubble bar expanded view size is used before first bubble

When querying the bubble bar expanded view bounds from BubblePositioner,
before a bubble is added, we are returning landscape floating bubble
size.
Only when bubble bar is active, are we returning the bubble bar expanded
view size.
Update this to ensure that even before the first bubble,
getBubbleBarExpandedViewBounds does return bounds for bubble bar
expanded view.
This is needed for dragging the first bubble into bubble bar and showing
the drop target, which is calculated based on bubble bar expanded view
size.

Bug: 388851898
Test: atest BubblePositionerTest
Flag: EXEMPT refactor
Change-Id: Ied9cf2e03bb818c3bf892febe5bd13abe0a2da10