Revert "Handle theme changes"

This reverts commit 64718d775ce8322915d143adb9a0f1ea3160e9e3.

Change-Id: Ibf92232dfa8ee96aafecc4b4e49fc55cfb21c229
Use wallpaper picker added to WallpaperCropper apk.

The code is still here for easier upstream merges.

Change-Id: I97ec1492e8acf7ff6a5ceef00a68f47e6444bf50