Resynthesize constructor initializers from Kernel.

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 1e7f8762dad21bfac4914cee9da505ba20a35bdc..8a602423bcc1d715c58626d0e519b679e94adf8e 100644
--- a/pkg/kernel/lib/binary/ast_from_binary.dart
+++ b/pkg/kernel/lib/binary/ast_from_binary.dart
@@ -626,15 +626,20 @@ class BinaryBuilder {
 
   Initializer readInitializer() {
     int tag = readByte();
+    bool isSynthetic = readByte() == 1;
     switch (tag) {
       case Tag.InvalidInitializer:
         return new InvalidInitializer();
       case Tag.FieldInitializer:
-        return new FieldInitializer.byReference(
-            readMemberReference(), readExpression());
+        var reference = readMemberReference();
+        var value = readExpression();
+        return new FieldInitializer.byReference(reference, value)
+          ..isSynthetic = isSynthetic;
       case Tag.SuperInitializer:
-        return new SuperInitializer.byReference(
-            readMemberReference(), readArguments());
+        var reference = readMemberReference();
+        var arguments = readArguments();
+        return new SuperInitializer.byReference(reference, arguments)
+          ..isSynthetic = isSynthetic;
       case Tag.RedirectingInitializer:
         return new RedirectingInitializer.byReference(
             readMemberReference(), readArguments());