[kernel] Add fileOffset on FunctionExpression

pkg/kernel/lib/binary/ast_to_binary.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_binary;
 
 import '../ast.dart';
 import '../import_table.dart';
 import 'tag.dart';
 import 'dart:convert';
 import 'dart:typed_data';
@@ skipping 811 matching lines @@
     writeNode(node.value);
   }
 
   visitAwaitExpression(AwaitExpression node) {
     writeByte(Tag.AwaitExpression);
     writeNode(node.operand);
   }
 
   visitFunctionExpression(FunctionExpression node) {
     writeByte(Tag.FunctionExpression);
+    writeOffset(node.fileOffset);
     writeNode(node.function);
   }
 
   visitLet(Let node) {
     writeByte(Tag.Let);
     writeVariableDeclaration(node.variable);
     writeNode(node.body);
     --_variableIndexer.stackHeight;
   }
 
@@ skipping 708 matching lines @@
     _sink.add(_buffer.sublist(0, length));
     _buffer = new Uint8List(SIZE);
     flushedLength += length;
     length = 0;
   }
 
   void flushAndDestroy() {
     _sink.add(_buffer.sublist(0, length));
   }
 }