Make homepage search bar remain persistent when scrolling

- Modify the scroll flag
- Add a background to avoid overlapping

Fix: 218825541
Test: visual
Change-Id: Ice88c1bb324780e72332dd810e654b1d17daafae
Merged-in: Ice88c1bb324780e72332dd810e654b1d17daafae
(cherry picked from commit 7cf0819b)