Fix several element properties in serialization.

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

 // Copyright (c) 2015, 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 dart2js.serialization.elements;
 
 import '../common.dart';
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../dart_types.dart';
@@ skipping 460 matching lines @@
     encoder.setString(Key.NAME, element.name);
     SerializerUtil.serializePosition(element, encoder);
     SerializerUtil.serializeParameters(element, encoder);
     encoder.setType(Key.TYPE, element.type);
     if (element.isFunction) {
       encoder.setBool(Key.IS_OPERATOR, element.isOperator);
       encoder.setEnum(Key.ASYNC_MARKER, element.asyncMarker);
     }
     SerializerUtil.serializeParentRelation(element, encoder);
     encoder.setBool(Key.IS_EXTERNAL, element.isExternal);
+    encoder.setBool(Key.IS_ABSTRACT, element.isAbstract);
     if (element.isLocal) {
       LocalFunctionElement localFunction = element;
       encoder.setElement(
           Key.EXECUTABLE_CONTEXT, localFunction.executableContext);
     }
   }
 }
 
 class TypedefSerializer implements ElementSerializer {
   const TypedefSerializer();
@@ skipping 239 matching lines @@
         return new LocalVariableElementZ(decoder);
       case SerializedElementKind.EXTERNAL_LIBRARY:
       case SerializedElementKind.EXTERNAL_LIBRARY_MEMBER:
       case SerializedElementKind.EXTERNAL_CLASS_MEMBER:
       case SerializedElementKind.EXTERNAL_CONSTRUCTOR:
         break;
     }
     throw new UnsupportedError("Unexpected element kind '${elementKind}.");
   }
 }