dart2js: add support for configuration-specific imports.

pkg/compiler/lib/src/parser/partial_parser.dart

Index: pkg/compiler/lib/src/parser/partial_parser.dart
diff --git a/pkg/compiler/lib/src/parser/partial_parser.dart b/pkg/compiler/lib/src/parser/partial_parser.dart
index 01de07c85a3ab0e1c0c251e2935515f5aefc79ab..1c7722f881d7c82c9baf3f9101a8b717169a071e 100644
--- a/pkg/compiler/lib/src/parser/partial_parser.dart
+++ b/pkg/compiler/lib/src/parser/partial_parser.dart
@@ -20,7 +20,9 @@ import 'parser.dart' show
     Parser;
 
 class PartialParser extends Parser {
-  PartialParser(Listener listener) : super(listener);
+  PartialParser(Listener listener, {bool enableConditionalDirectives})
+      : super(listener,
+          enableConditionalDirectives: enableConditionalDirectives);
 
   Token parseClassBody(Token token) => skipClassBody(token);