Change Link to List in FunctionSignature.

pkg/compiler/lib/src/resolution/members.dart

Index: pkg/compiler/lib/src/resolution/members.dart
diff --git a/pkg/compiler/lib/src/resolution/members.dart b/pkg/compiler/lib/src/resolution/members.dart
index f2ea645eb06e0da7776e33ac1a64a8112822b415..a3420a3b739ae1cdafc53225fbd20c45381a89e1 100644
--- a/pkg/compiler/lib/src/resolution/members.dart
+++ b/pkg/compiler/lib/src/resolution/members.dart
@@ -2407,8 +2407,8 @@ class ResolverVisitor extends MappingVisitor<ResolutionResult> {
     functionParameters.forEachParameter((ParameterElement element) {
       // TODO(karlklose): should be a list of [FormalElement]s, but the actual
       // implementation uses [Element].
-      Link<Element> optionals = functionParameters.optionalParameters;
-      if (!optionals.isEmpty && element == optionals.head) {
+      List<Element> optionals = functionParameters.optionalParameters;
+      if (!optionals.isEmpty && element == optionals.first) {
         NodeList nodes = parameterNodes.head;
         parameterNodes = nodes.nodes;
       }