Render user's actual workspace in ThemePicker preview (Part 2)

With this change, we can also render folders in preview. It's built on top of part 1.

Test: Go to grid options, choose a different grid option, and see user's workspace rendered in the preview
Bug: 144052839
Change-Id: Iaf6d8af6b909ece4147ea250d95dec3d2c0019d3
6 files changed