Emit compile-time error on 'const' formal parameters.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index 9e5f039b60fe043b33df7893d827c349d3bae185..75aa1cbee80c0ab6e487a7b577ea7b7babc4ea07 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -3995,6 +3995,9 @@ class SignatureResolver extends CommonResolverVisitor<Element> {
     if (definition is NodeList) {
       cancel(node, 'optional parameters are not implemented');
     }
+    if (node.modifiers.isConst()) {
+      error(node, MessageKind.FORMAL_DECLARED_CONST);
+    }
 
     if (currentDefinitions != null) {
       cancel(node, 'function type parameters not supported');