Replace field injection with constructor  injection. am: 4530819818

Original change: https://android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/3343446

Change-Id: Iec31c2ab87bdae090760364bb1f2ee9339536909
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>