Rebased and retested version of CL 1915123008.

pkg/compiler/lib/src/serialization/resolved_ast_serialization.dart

Index: pkg/compiler/lib/src/serialization/resolved_ast_serialization.dart
diff --git a/pkg/compiler/lib/src/serialization/resolved_ast_serialization.dart b/pkg/compiler/lib/src/serialization/resolved_ast_serialization.dart
index bac31b1becdca220c2ea06de025557aa5856e2e1..047f4b6af23ac4cdaf512d8f2ead72bdf00207eb 100644
--- a/pkg/compiler/lib/src/serialization/resolved_ast_serialization.dart
+++ b/pkg/compiler/lib/src/serialization/resolved_ast_serialization.dart
@@ -429,6 +429,7 @@ class ResolvedAstDeserializer {
           FunctionExpression toStringNode = builder.functionExpression(
               Modifiers.EMPTY,
               'toString',
+              null,
               builder.argumentList([]),
               builder.returnStatement(builder.indexGet(
                   builder.mapLiteral(mapEntries, isConst: true),
@@ -441,6 +442,7 @@ class ResolvedAstDeserializer {
           FunctionExpression constructorNode = builder.functionExpression(
               builder.modifiers(isConst: true),
               element.enclosingClass.name,
+              null,
               builder.argumentList([indexDefinition]),
               builder.emptyStatement());
           return constructorNode;