move => bind this workaround to js_ast

lib/src/js/printer.dart

 // Copyright (c) 2012, 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.
 
 part of js_ast;
 
 
 class JavaScriptPrintingOptions {
   final bool shouldCompressOutput;
   final bool minifyLocalVariables;
@@ skipping 806 matching lines @@
 
   visitNamedFunction(NamedFunction namedFunction) {
     functionOut(namedFunction.function, namedFunction.name, namedFunction);
   }
 
   visitFun(Fun fun) {
     functionOut(fun, null, fun);
   }
 
   visitArrowFun(ArrowFun fun) {
+    if (fun.bindThisWorkaround) {
+      out("(");
+    }
     localNamer.enterScope(fun);
     out("(");
     if (fun.params != null) {
       visitCommaSeparated(fun.params, PRIMARY,
           newInForInit: false, newAtStatementBegin: false);
     }
     out(")");
     spaceOut();
     out("=>");
     if (fun.body is Expression) {
       spaceOut();
       fun.body.accept(this);
     } else {
       blockBody(fun.body, needsSeparation: false, needsNewline: false);
     }
     localNamer.leaveScope();
+    if (fun.bindThisWorkaround) {
+      out(").bind(this)");
+    }
   }
 
   visitLiteralBool(LiteralBool node) {
     out(node.value ? "true" : "false");
   }
 
   visitLiteralString(LiteralString node) {
     out(node.value);
   }
 
@@ skipping 512 matching lines @@
         codes.add(nthLetter((n ~/ nameSpaceSize) % LETTERS));
       }
       codes.add(charCodes.$0 + digit);
       newName = new String.fromCharCodes(codes);
     }
     assert(new RegExp(r'[a-zA-Z][a-zA-Z0-9]*').hasMatch(newName));
     maps.last[oldName] = newName;
     return newName;
   }
 }