Add support for arc-length metric in variable width stroke sample
Add support for arc-length metric in variable width stroke sample

I left in the ability to swap between using % arc length versus dividing
t evenly up across path segments so we can easily visually compare the
effect.

Change-Id: Id83792aa9e22fd5464e956092bac0baec389ffed
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/330103
Reviewed-by: Chris Dalton <ef7fc3a08ada7d31f16e9a18b5f3c728256e041e@google.com>
Commit-Queue: Tyler Denniston <293ae2d31b7e9da32c4fb58bdaaed1f4bef4c6e7@google.com>

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