Optimize splitting lines with many rules.

lib/src/line_splitting/rule_set.dart

Index: lib/src/line_splitting/rule_set.dart
diff --git a/lib/src/line_splitting/rule_set.dart b/lib/src/line_splitting/rule_set.dart
index 709b3739e671db0c1e2188e14ddd551ca5e82eb7..e0cf3e181c82fbe19783747dcba87cfefeafaa73 100644
--- a/lib/src/line_splitting/rule_set.dart
+++ b/lib/src/line_splitting/rule_set.dart
@@ -59,9 +59,7 @@ class RuleSet {
     _values[rule.index] = value;
 
     // Test this rule against the other rules being bound.
-    for (var other in rules) {
-      if (rule == other) continue;
-
+    for (var other in rule.constrainedRules) {
       var otherValue = _values[other.index];
       var constraint = rule.constrain(value, other);