Change Link to List in FunctionSignature.

pkg/compiler/lib/src/util/link.dart

Index: pkg/compiler/lib/src/util/link.dart
diff --git a/pkg/compiler/lib/src/util/link.dart b/pkg/compiler/lib/src/util/link.dart
index 648e185cdbc7b356081a5ba05bb398cbcedb7116..b45ea6cd5bb3508043b96419fe4357afdc94ee29 100644
--- a/pkg/compiler/lib/src/util/link.dart
+++ b/pkg/compiler/lib/src/util/link.dart
@@ -56,16 +56,6 @@ class Link<T> {
     return result;
   }
 
-  /// Invokes `fn` for every item in the linked list and returns the results
-  /// in a [Set].
-  Set mapToSet(dynamic fn(T item)) {
-    Set result = new Set();
-    for (Link<T> link = this; !link.isEmpty; link = link.tail) {
-      result.add(fn(link.head));
-    }
-    return result;
-  }
-
   bool get isEmpty => true;
 
   Link<T> reverse() => this;