Fix mass property update when adding a collider.

src/geometry/collider.rs

@@ -150,6 +150,7 @@ impl Collider {
     }
 
     /// The position of this collider expressed in the local-space of the rigid-body it is attached to.
+    #[deprecated(note = "use `.position_wrt_parent()` instead.")]
     pub fn delta(&self) -> &Isometry<f32> {
         &self.delta
     }

src/geometry/contact.rs

@@ -360,8 +360,8 @@ impl ContactManifold {
             pair,
             (subshape1, subshape2),
             BodyPair::new(coll1.parent, coll2.parent),
-            *coll1.delta(),
-            *coll2.delta(),
+            *coll1.position_wrt_parent(),
+            *coll2.position_wrt_parent(),
             (coll1.friction + coll2.friction) * 0.5,
             (coll1.restitution + coll2.restitution) * 0.5,
         )