Reduce affinity confusion

LayoutNode.js

@@ -44,7 +44,7 @@ class LayoutNode {
       // If so, preserve one space above the group
       let labeled = new Set(Array.from(this.groups).filter(g => !!g.label));
       if (asymDifference(labeled, node.groups).size) {
-        node.addAffinity(this, (d, v) =>
+        this.addAffinity(node, (d, v) =>
                          (v[0] == 0 && v[1] > 0 && v[1] < 2) ? -INF : 0);
       }
 
@@ -65,10 +65,7 @@ class LayoutNode {
         if (group.nodes.has(node)) {
           continue;
         }
-        this.affinity_.push({
-          node: node,
-          distanceToWeight: (d, v, p) => group.isContained(p) ? -INF : 0,
-        });
+        this.addAffinity(node, (d, v, p) => group.isContained(p) ? -INF : 0);
       }
     }