[Kernel] replace function debuggable field with originalAsyncMarker field

pkg/kernel/lib/text/ast_to_text.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 library kernel.ast_to_text;
 
 import '../ast.dart';
 import '../import_table.dart';
 import '../type_propagation/type_propagation.dart';
 
 class Namer<T> {
@@ skipping 481 matching lines @@
       endLine();
       ++indentation;
       writeIndentation();
       writeComma(':');
       writeList(initializers, writeNode);
       --indentation;
     }
     if (function.asyncMarker != AsyncMarker.Sync) {
       writeSpaced(getAsyncMarkerKeyword(function.asyncMarker));
     }
-    if (!function.debuggable) writeSpaced("/* not debuggable */");
+    if (function.originalAsyncMarker != AsyncMarker.Sync) {
+      writeSpaced("/* originally");
+      writeSpaced(getAsyncMarkerKeyword(function.originalAsyncMarker));
+      writeSpaced("*/");
+    }
     if (function.body != null) {
       writeFunctionBody(function.body, terminateLine: terminateLine);
     } else if (terminateLine) {
       endLine(';');
     }
   }
 
   String getAsyncMarkerKeyword(AsyncMarker marker) {
     switch (marker) {
       case AsyncMarker.Sync:
@@ skipping 1074 matching lines @@
   }
   throw 'illegal ProcedureKind: $kind';
 }
 
 class ExpressionPrinter {
   final Printer writeer;
   final int minimumPrecedence;
 
   ExpressionPrinter(this.writeer, this.minimumPrecedence);
 }