BottomSheet slideOffset when peekHeight is auto

As we introduced PEEK_HEIGHT_AUTO, we cannot rely on mPeekHeight to have
a meaninful value. Use mParentHeight and mMaxOffset instead as they are
always dynamically calculated values.

Bug: 31208971
Change-Id: Ic7d9f521faf6993a7c6e86357d4beb23e5e39137
2 files changed