VM: Evaluate metadata on a class in the scope of its library not the scope of the class.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 80b621e15d6a04fe663dad468f2dad4ded9b698e..5f448e39b659cf08e7619c187306948c5a0cc009 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -8033,8 +8033,14 @@ void Library::AddMetadata(const Class& cls,
 }
 
 
-void Library::AddClassMetadata(const Class& cls, intptr_t token_pos) const {
-  AddMetadata(cls, String::Handle(MakeClassMetaName(cls)), token_pos);
+void Library::AddClassMetadata(const Class& cls,
+                               const Class& toplevel_class,
+                               intptr_t token_pos) const {
+  // We use the toplevel class as the owner of a class's metadata field because
+  // a class's metadata is in scope of the library, not the class.
+  AddMetadata(toplevel_class,
+              String::Handle(MakeClassMetaName(cls)),
+              token_pos);
 }