Fix LibraryDependencyMirrors when the target is a native extension.

runtime/lib/mirrors.cc

 // 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.
 
 #include "lib/mirrors.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
@@ skipping 428 matching lines @@
   }
 
   Object& metadata = Object::Handle(ns.GetMetadata());
   if (metadata.IsError()) {
     Exceptions::PropagateError(Error::Cast(metadata));
     UNREACHABLE();
   }
 
   const Array& args = Array::Handle(Array::New(7));
   args.SetAt(0, importer);
-  args.SetAt(1, importee.Loaded() ? importee_mirror : prefix);
+  if (importee.Loaded() || prefix.IsNull()) {
+    // A native extension is never "loaded" by the embedder. Use the fact that
+    // it doesn't have an prefix where asa  deferred import does to distinguish
+    // it from a deferred import. It will appear like an empty library.
+    args.SetAt(1, importee_mirror);
+  } else {
+    args.SetAt(1, prefix);
+  }
   args.SetAt(2, combinators);
   args.SetAt(3, prefix.IsNull() ? Object::null_object()
                                 : String::Handle(prefix.name()));
   args.SetAt(4, Bool::Get(is_import));
   args.SetAt(5, Bool::Get(is_deferred));
   args.SetAt(6, metadata);
   return CreateMirror(Symbols::_LocalLibraryDependencyMirror(), args);
 }
 
 
@@ skipping 1627 matching lines @@
 
 DEFINE_NATIVE_ENTRY(TypeMirror_subtypeTest, 2) {
   GET_NON_NULL_NATIVE_ARGUMENT(AbstractType, a, arguments->NativeArgAt(0));
   GET_NON_NULL_NATIVE_ARGUMENT(AbstractType, b, arguments->NativeArgAt(1));
   return Bool::Get(a.IsSubtypeOf(b, NULL, NULL, Heap::kNew)).raw();
 }
 
 #endif  // !PRODUCT && !DART_PRECOMPILED_RUNTIME
 
 }  // namespace dart