Add optional FunctionType.positionalParameterNames and use them to resynthesize function-type forma…

pkg/kernel/lib/binary/ast_to_binary.dart

Index: pkg/kernel/lib/binary/ast_to_binary.dart
diff --git a/pkg/kernel/lib/binary/ast_to_binary.dart b/pkg/kernel/lib/binary/ast_to_binary.dart
index 16d7f0cc8c9bf01c6e6b3918f0130da4936a5477..9cf4b7058a8e7ad069775b6ddcef585bee5907c5 100644
--- a/pkg/kernel/lib/binary/ast_to_binary.dart
+++ b/pkg/kernel/lib/binary/ast_to_binary.dart
@@ -1115,6 +1115,7 @@ class BinaryPrinter extends Visitor {
         node.namedParameters.isEmpty) {
       writeByte(Tag.SimpleFunctionType);
       writeNodeList(node.positionalParameters);
+      writeStringReferenceList(node.positionalParameterNames);
       writeNode(node.returnType);
     } else {
       writeByte(Tag.FunctionType);
@@ -1125,6 +1126,7 @@ class BinaryPrinter extends Visitor {
           node.positionalParameters.length + node.namedParameters.length);
       writeNodeList(node.positionalParameters);
       writeNodeList(node.namedParameters);
+      writeStringReferenceList(node.positionalParameterNames);
       writeNode(node.returnType);
       _typeParameterIndexer.exit(node.typeParameters);
     }
@@ -1385,6 +1387,12 @@ class StringIndexer extends RecursiveVisitor<Null> {
     super.visitField(node);
   }
 
+  @override
+  visitFunctionType(FunctionType node) {
+    node.positionalParameterNames.forEach(put);
+    super.visitFunctionType(node);
+  }
+
   visitNamedExpression(NamedExpression node) {
     put(node.name);
     node.visitChildren(this);