restore arrow function bind this workaround

lib/src/codegen/js_printer.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 dev_compiler.src.codegen.js_printer;
 
 import 'dart:io' show Directory, File;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:path/path.dart' as path;
 import 'package:source_maps/source_maps.dart' as srcmaps show Printer;
 import 'package:source_maps/source_maps.dart' show SourceMapSpan;
 import 'package:source_span/source_span.dart' show SourceLocation;
 
 import 'package:dev_compiler/src/js/js_ast.dart' as JS;
 import 'package:dev_compiler/src/utils.dart'
     show computeHash, locationForOffset;
 
 import 'js_names.dart' show TemporaryNamer;
 
 String writeJsLibrary(JS.Program jsTree, String outputPath,
-    {bool emitSourceMaps: false}) {
-  new Directory(path.dirname(outputPath)).createSync(recursive: true);
+    {bool emitSourceMaps: false, bool arrowFnBindThisWorkaround: false}) {
+  var outFilename = path.basename(outputPath);
+  var outDir = path.dirname(outputPath);
+  new Directory(outDir).createSync(recursive: true);
+
+  JS.JavaScriptPrintingContext context;
   if (emitSourceMaps) {
-    var outFilename = path.basename(outputPath);
     var printer = new srcmaps.Printer(outFilename);
-    writeNodeToContext(jsTree,
-        new SourceMapPrintingContext(printer, path.dirname(outputPath)));
+    context = new SourceMapPrintingContext(printer, outDir);
+  } else {
+    context = new JS.SimpleJavaScriptPrintingContext();
+  }
+
+  var opts = new JS.JavaScriptPrintingOptions(
+      allowKeywordsInProperties: true,
+      arrowFnBindThisWorkaround: arrowFnBindThisWorkaround);
+  var jsNamer = new TemporaryNamer(jsTree);
+  jsTree.accept(new JS.Printer(opts, context, localNamer: jsNamer));
+
+  String text;
+  if (context is SourceMapPrintingContext) {
+    var printer = context.printer;
     printer.add('//# sourceMappingURL=$outFilename.map');
     // Write output file and source map
-    var text = printer.text;
-    new File(outputPath).writeAsStringSync(text);
+    text = printer.text;
     new File('$outputPath.map').writeAsStringSync(printer.map);
-    return computeHash(text);
   } else {
-    var text = jsNodeToString(jsTree);
-    new File(outputPath).writeAsStringSync(text);
-    return computeHash(text);
+    text = (context as JS.SimpleJavaScriptPrintingContext).getText();
   }
-}
-
-void writeNodeToContext(JS.Node node, JS.JavaScriptPrintingContext context) {
-  var opts = new JS.JavaScriptPrintingOptions(allowKeywordsInProperties: true);
-  node.accept(
-      new JS.Printer(opts, context, localNamer: new TemporaryNamer(node)));
-}
-
-String jsNodeToString(JS.Node node) {
-  var context = new JS.SimpleJavaScriptPrintingContext();
-  writeNodeToContext(node, context);
-  return context.getText();
+  new File(outputPath).writeAsStringSync(text);
+  return computeHash(text);
 }
 
 class SourceMapPrintingContext extends JS.JavaScriptPrintingContext {
   final srcmaps.Printer printer;
   final String outputDir;
 
   CompilationUnit unit;
   Uri uri;
 
   SourceMapPrintingContext(this.printer, this.outputDir);
@@ skipping 41 matching lines @@
 
     // TODO(jmesserly): in many cases marking the end will be unnecessary.
     printer.mark(_location(node.end));
   }
 
   String _getIdentifier(AstNode node) {
     if (node is SimpleIdentifier) return node.name;
     return null;
   }
 }