Propagate canUseNative flag to synthesized library.

lib/compiler/implementation/unparse_validator.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class ValidatorListener implements DiagnosticListener {
   final SourceFile sourceFile;
 
   ValidatorListener(this.sourceFile);
 
   void cancel([String reason, node, token, instruction, element]) {
@@ skipping 41 matching lines @@
     // TODO(ahe): This is also too frigging complicated.
     Script originalScript = element.getCompilationUnit().script;
     String name = SourceSpan.withOffsets(
         originalFunction.beginToken, originalFunction.endToken,
         (beginOffset, endOffset) =>
             'synthesized:${originalScript.name}#$beginOffset:$endOffset');
     SourceFile synthesizedSourceFile = new SourceFile(name, unparsed);
     Script synthesizedScript =
         new Script(originalScript.uri, synthesizedSourceFile);
     LibraryElement lib = new LibraryElement(synthesizedScript);
+    lib.canUseNative = element.getLibrary().canUseNative;
     NodeListener listener =
         new NodeListener(new ValidatorListener(synthesizedSourceFile), lib);
     parser = new Parser(listener);
     parser.parseFunction(newTokens, getOrSet);
     FunctionExpression newNode = listener.popNode();
     // TODO(antonm): add Node comparison.
   }
 }