Return mSynchronouslyBoundPages as getPagesToBindSynchronously between...

Return mSynchronouslyBoundPages as getPagesToBindSynchronously between onInitialBindCompleteand finishBindingItems

- Otherwise it'll return wrong currentPage value, as currentPage aren't updated until finishBindingItems
- There is still problem that wallpaper jumps to page 0 and then to the desired page: https://drive.google.com/file/d/132Sq5oRZKRclhdh1Ls1RaHNEVXJQcrxC/view?usp=sharing&resourcekey=0-l2N9NWtZ8FqfaVT0bVGVqw

Bug: 191657065
Test: manual
Change-Id: I7ec167b617a8f59865e959d9dd677256b1ab4ef9