Update assertion in finalizer

runtime/vm/class_finalizer.cc

 // Copyright (c) 2013, 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 "vm/class_finalizer.h"
 
 #include "vm/code_generator.h"
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
@@ skipping 2500 matching lines @@
 
     const Class& mixin_app_class = Class::Handle(cls.SuperClass());
     const Type& mixin_type = Type::Handle(mixin_app_class.mixin());
     const Class& mixin_cls = Class::Handle(mixin_type.type_class());
 
     CreateForwardingConstructors(cls, mixin_cls, cloned_funcs);
     const Array& functions = Array::Handle(Array::MakeArray(cloned_funcs));
     cls.SetFunctions(functions);
   }
   // Every class should have at least a constructor, unless it is a top level
-  // class or a typedef class.
-  ASSERT(cls.IsTopLevel() || cls.IsTypedefClass() ||
+  // class or a typedef class. The Kernel frontend does not create an implicit
+  // constructor for abstract classes.
+  ASSERT(cls.IsTopLevel() || cls.IsTypedefClass() || cls.is_abstract() ||
          (Array::Handle(cls.functions()).Length() > 0));
   // Resolve and finalize all member types.
   ResolveAndFinalizeMemberTypes(cls);
   // Run additional checks after all types are finalized.
   if (cls.is_const()) {
     CheckForLegalConstClass(cls);
   }
   if (FLAG_use_cha_deopt) {
     GrowableArray<intptr_t> cids;
     CollectFinalizedSuperClasses(cls, &cids);
@@ skipping 857 matching lines @@
   ASSERT(fields_array.Length() == ByteBuffer::NumberOfFields());
   field ^= fields_array.At(0);
   ASSERT(field.Offset() == ByteBuffer::data_offset());
   name ^= field.name();
   expected_name ^= String::New("_data");
   ASSERT(String::EqualsIgnoringPrivateKey(name, expected_name));
 #endif
 }
 
 }  // namespace dart