Fix missing functionality with --allow-native-extensions

pkg/compiler/lib/src/native/native.dart

Index: pkg/compiler/lib/src/native/native.dart
diff --git a/pkg/compiler/lib/src/native/native.dart b/pkg/compiler/lib/src/native/native.dart
index 9a8140183bde92999d6018aac913946a8fb3d058..c9c60f6996e120409a3498f7e132ff6892d00c24 100644
--- a/pkg/compiler/lib/src/native/native.dart
+++ b/pkg/compiler/lib/src/native/native.dart
@@ -38,5 +38,7 @@ bool maybeEnableNative(Compiler compiler, LibraryElement library) {
     return _allowedDartSchemePaths.contains(uri.path);
   }
 
-  return allowedTestLibrary() || allowedDartLibary();
+  return allowedTestLibrary() ||
+      allowedDartLibary() ||
+      compiler.options.allowNativeExtensions;
 }