Separate stroke-length code into static functions am: cf709f207d

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libpalmrejection/+/19914652

Change-Id: Id76fdd6dd3c885cbbca3eca9f1914a97d02c327f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>