Fix unparse for empty initializer or conditionStatement.

lib/compiler/implementation/tree/unparser.dart

Index: lib/compiler/implementation/tree/unparser.dart
diff --git a/lib/compiler/implementation/tree/unparser.dart b/lib/compiler/implementation/tree/unparser.dart
index cf0911d10f4728d673d6c54d0471de76a8640fd3..a4bf8c8e6bcc333f0bc4f83a7ecb368f65ce13ea 100644
--- a/lib/compiler/implementation/tree/unparser.dart
+++ b/lib/compiler/implementation/tree/unparser.dart
@@ -76,8 +76,15 @@ class Unparser implements Visitor {
   visitFor(For node) {
     add(node.forToken.value);
     sb.add('(');
-    visit(node.initializer);
-    visit(node.conditionStatement);
+    visitPart(part) {

[Anton Muhin, 2012/06/07 15:31:29]

another option would be to yield empty statements out of parser for those.

+      if (part === null) {
+        sb.add(';');
+      } else {
+        visit(part);
+      }
+    }
+    visitPart(node.initializer);
+    visitPart(node.conditionStatement);
     visit(node.update);
     sb.add(')');
     visit(node.body);