Use closure conversion in new dart2js backend.

pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart
index 1a162c83e797bb244698aa21b2df7710e5cf5380..0e6dd308d5a7fb88f9e4b2a3ef047614777fbb30 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart
@@ -228,6 +228,30 @@ class SExpressionStringifier extends Visitor<String> with Indentation {
     return '(IsTrue $value)';
   }
 
+  String visitSetField(SetField node) {
+    String object = access(node.object);
+    String field = node.field.name;
+    String value = access(node.value);
+    String body = indentBlock(() => visit(node.body));
+    return '$indentation(SetField $object.$field = $value in\n$body)';

[Kevin Millikin (Google), 2015/01/13 08:25:36]

I don't really want '.', '=', or 'in' here.  This representation is abstract
syntax, and they just make parsing harder.

Though the expression has a body, it's not really a scope (setting a field is
assignment, not binding).  I'd prefer it formatted like setq in Lisp or set! in
Scheme:

String body = visit(node.body);
return '$indentation(SetField $object $field $value)\n$body';

[asgerf, 2015/01/13 10:04:26]

Yeah, I must have been half-thinking about the IR tracer when I wrote this.

+  }
+
+  String visitGetField(GetField node) {
+    String object = access(node.object);
+    String field = node.field.toString();
+    return '(GetField $object.$field)';

[Kevin Millikin (Google), 2015/01/13 08:25:36]

No dot:

'(GetField $object $field)'

+  }
+
+  String visitCreateBox(CreateBox node) {
+    return '(CreateBox)';
+  }
+
+  String visitCreateClosureClass(CreateClosureClass node) {
+    String className = node.classElement.name;
+    String arguments = node.arguments.map(access).join(' ');
+    return '(CreateClosureClass $className $arguments)';

[Kevin Millikin (Google), 2015/01/13 08:25:36]

'(CreateClosureClass $className ($arguments))'

+  }
+
   String visitIdentical(Identical node) {
     String left = access(node.left);
     String right = access(node.right);