Resynthesize constructor initializers from Kernel.

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 b1a55e58ba29b308fea6ec75e91bdc2ad28206b4..28bb9fd936eda9a937a0f4b97c5861591424e2c7 100644
--- a/pkg/kernel/lib/binary/ast_to_binary.dart
+++ b/pkg/kernel/lib/binary/ast_to_binary.dart
@@ -475,28 +475,33 @@ class BinaryPrinter extends Visitor {
 
   visitInvalidInitializer(InvalidInitializer node) {
     writeByte(Tag.InvalidInitializer);
+    writeByte(node.isSynthetic ? 1 : 0);
   }
 
   visitFieldInitializer(FieldInitializer node) {
     writeByte(Tag.FieldInitializer);
+    writeByte(node.isSynthetic ? 1 : 0);
     writeReference(node.fieldReference);
     writeNode(node.value);
   }
 
   visitSuperInitializer(SuperInitializer node) {
     writeByte(Tag.SuperInitializer);
+    writeByte(node.isSynthetic ? 1 : 0);
     writeReference(node.targetReference);
     writeNode(node.arguments);
   }
 
   visitRedirectingInitializer(RedirectingInitializer node) {
     writeByte(Tag.RedirectingInitializer);
+    writeByte(node.isSynthetic ? 1 : 0);
     writeReference(node.targetReference);
     writeNode(node.arguments);
   }
 
   visitLocalInitializer(LocalInitializer node) {
     writeByte(Tag.LocalInitializer);
+    writeByte(node.isSynthetic ? 1 : 0);
     writeVariableDeclaration(node.variable);
   }