minor fm_driver tweaks
minor fm_driver tweaks

Move definition of Work struct until just before it's used,
and show one of the sources as an example at kickoff-level step.

These are just cosmetic/refactors.

Change-Id: Ib23b9379683b9867e097c8d68ef8736013719cee
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/369356
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia