Fix path bug in windows, don't emit code altogether if we have already seen

lib/src/dart_parser.dart

Index: lib/src/dart_parser.dart
diff --git a/lib/src/dart_parser.dart b/lib/src/dart_parser.dart
index b3896d4d7570a026242fe578105f2c8f63e08d6e..fa1e68a352a40489a4bbddced28e50119c42443d 100644
--- a/lib/src/dart_parser.dart
+++ b/lib/src/dart_parser.dart
@@ -140,6 +140,8 @@ CompilationUnit parseCompilationUnit(String code, {String path,
   // messages properly, so you end up with things like "Unexpected token '%s'".
   // This used to convert parser messages into our messages. Enable this
   // once analyzer is fixed.
+  // TODO(sigmund): once we enable this, we need to fix compiler.dart to clear
+  // out the output of the compiler if we see compilation errors.
   if (false) {
     var file = new File.text(path, code);
     for (var e in errorListener.errors) {