dart2js: add support for configuration-specific imports.

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

Index: pkg/compiler/lib/src/parser/parser_task.dart
diff --git a/pkg/compiler/lib/src/parser/parser_task.dart b/pkg/compiler/lib/src/parser/parser_task.dart
index b9d89ef6f77437e71404a13c9544e26af0f3ec47..2f7c7c926280b0f44efa01f576c762ec73bed3f7 100644
--- a/pkg/compiler/lib/src/parser/parser_task.dart
+++ b/pkg/compiler/lib/src/parser/parser_task.dart
@@ -25,7 +25,13 @@ import 'parser.dart' show
     Parser;
 
 class ParserTask extends CompilerTask {
-  ParserTask(Compiler compiler) : super(compiler);
+  final bool _enableConditionalDirectives;
+
+  ParserTask(Compiler compiler,
+             {bool enableConditionalDirectives: false})
+      : this._enableConditionalDirectives = enableConditionalDirectives,
+        super(compiler);
+
   String get name => 'Parser';
 
   Node parse(ElementX element) {
@@ -35,7 +41,9 @@ class ParserTask extends CompilerTask {
   Node parseCompilationUnit(Token token) {
     return measure(() {
       NodeListener listener = new NodeListener(compiler, null);
-      Parser parser = new Parser(listener);
+      print("parser: $_enableConditionalDirectives");

[Johnni Winther, 2015/10/14 07:21:52]

Remove debug code.

[floitsch, 2015/12/10 19:38:43]

Done.

+      Parser parser = new Parser(
+          listener, enableConditionalDirectives: _enableConditionalDirectives);
       try {
         parser.parseUnit(token);
       } on ParserError catch(_) {