Remove signature classes from the VM.

runtime/vm/cha_test.cc

Index: runtime/vm/cha_test.cc
diff --git a/runtime/vm/cha_test.cc b/runtime/vm/cha_test.cc
index a7c998df3999b576aad8bcb9885e8bb829b26ee6..771232467fc3c448d4ba6485b9a449a5a0498601 100644
--- a/runtime/vm/cha_test.cc
+++ b/runtime/vm/cha_test.cc
@@ -98,10 +98,9 @@ TEST_CASE(ClassHierarchyAnalysis) {
   EXPECT(ContainsCid(cha.leaf_classes(), class_c.id()));
   EXPECT(ContainsCid(cha.leaf_classes(), class_d.id()));
 
-  const Class& function_impl_class =
-      Class::Handle(Type::Handle(Isolate::Current()->object_store()->
-          function_impl_type()).type_class());
-  EXPECT(cha.HasSubclasses(function_impl_class.id()));
+  const Class& closure_class =
+      Class::Handle(Isolate::Current()->object_store()->closure_class());
+  EXPECT(!cha.HasSubclasses(closure_class.id()));
 }
 
 }  // namespace dart