Fix native extension lookup

runtime/bin/extensions.h

Index: runtime/bin/extensions.h
diff --git a/runtime/bin/extensions.h b/runtime/bin/extensions.h
index d26630363814eb93c30841a36207e334ddbac9b3..bcbcac3c7f834448bb0cc653814f8799e529ac32 100644
--- a/runtime/bin/extensions.h
+++ b/runtime/bin/extensions.h
@@ -26,6 +26,11 @@ class Extensions {
  private:
   static Dart_Handle GetError();
 
+  static void* MakePathAndResolve(const char* dir, const char* name);
+  static void* ResolveAbsPathExtension(const char* extension_path);
+  static void* ResolveExtension(const char* extensioion_directory,
+                                const char* extension_name);
+
   // The returned string is scope allocated.
   static const char* Concatenate(const char** strings);