Function writeback_collider_mass_properties 

pub fn writeback_collider_mass_properties(
    context_colliders: Query<'_, '_, &RapierContextColliders>,
    colliders: Query<'_, '_, (&RapierColliderHandle, &RapierContextEntityLink, &mut ReadColliderMassProperties), Or<(Added<RapierColliderHandle>, Added<ReadColliderMassProperties>, Changed<Collider>, Changed<ColliderMassProperties>)>>,
)

System responsible for writing the mass properties of colliders back into the ReadColliderMassProperties component.

This runs for colliders that were just created, or with a modified shape or ColliderMassProperties.