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

pkg/kernel/lib/binary/ast_from_binary.dart

Index: pkg/kernel/lib/binary/ast_from_binary.dart
diff --git a/pkg/kernel/lib/binary/ast_from_binary.dart b/pkg/kernel/lib/binary/ast_from_binary.dart
index 04c4b6906effe0196f76caa9b8db05de0f9b155e..25974b0122de9642dc7993f0cad79df82c6e047f 100644
--- a/pkg/kernel/lib/binary/ast_from_binary.dart
+++ b/pkg/kernel/lib/binary/ast_from_binary.dart
@@ -1162,17 +1162,21 @@ class BinaryBuilder {
         var totalParameterCount = readUInt();
         var positional = readDartTypeList();
         var named = readNamedTypeList();
+        var positionalNames = readStringReferenceList();
         assert(positional.length + named.length == totalParameterCount);
         var returnType = readDartType();
         typeParameterStack.length = typeParameterStackHeight;
         return new FunctionType(positional, returnType,
             typeParameters: typeParameters,
             requiredParameterCount: requiredParameterCount,
-            namedParameters: named);
+            namedParameters: named,
+            positionalParameterNames: positionalNames);
       case Tag.SimpleFunctionType:
         var positional = readDartTypeList();
+        var positionalNames = readStringReferenceList();
         var returnType = readDartType();
-        return new FunctionType(positional, returnType);
+        return new FunctionType(positional, returnType,
+            positionalParameterNames: positionalNames);
       case Tag.TypeParameterType:
         int index = readUInt();
         readUInt(); // offset of parameter list in the binary.