Eliminate fake-Isolate workaround from concurrent sweeper.

runtime/vm/raw_object.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 "vm/raw_object.h"
 
 #include "vm/class_table.h"
 #include "vm/dart.h"
 #include "vm/freelist.h"
 #include "vm/isolate.h"
@@ skipping 47 matching lines @@
     return;
   }
   intptr_t size = SizeTag::decode(tags);
   if (size != 0 && size != SizeFromClass()) {
     FATAL1("Inconsistent class size encountered %" Pd "\n", size);
   }
 }
 
 
 intptr_t RawObject::SizeFromClass() const {
-  Isolate* isolate = Isolate::Current();
-  NoHandleScope no_handles(isolate);
+  return SizeFromClass(Isolate::Current()->class_table());
+}
 
+
+intptr_t RawObject::SizeFromClass(const ClassTable* class_table) const {
   // Only reasonable to be called on heap objects.
   ASSERT(IsHeapObject());
 
   intptr_t class_id = GetClassId();
-  ClassTable* class_table = isolate->class_table();
 #if defined(DEBUG)
   if (!class_table->IsValidIndex(class_id) ||
       !class_table->HasValidClassAt(class_id)) {
     FATAL2("Invalid class id: %" Pd " from tags %" Px "\n",
            class_id, ptr()->tags_);
   }
 #endif  // DEBUG
   RawClass* raw_class = class_table->At(class_id);
   ASSERT(raw_class->ptr()->id_ == class_id);
 
@@ skipping 850 matching lines @@
 intptr_t RawUserTag::VisitUserTagPointers(
     RawUserTag* raw_obj, ObjectPointerVisitor* visitor) {
   // Make sure that we got here with the tagged pointer as this.
   ASSERT(raw_obj->IsHeapObject());
   visitor->VisitPointers(raw_obj->from(), raw_obj->to());
   return UserTag::InstanceSize();
 }
 
 
 }  // namespace dart