In generated code for ia32 don't load object's class directly from class_ field.

runtime/vm/class_table.h

 // 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.
 
 #ifndef VM_CLASS_TABLE_H_
 #define VM_CLASS_TABLE_H_
 
 #include "platform/assert.h"
 #include "platform/globals.h"
+#include "vm/globals.h"
 
 namespace dart {
 
 class Class;
 class ObjectPointerVisitor;
 class RawClass;
 
 class ClassTable {
  public:
   ClassTable();
   ~ClassTable();
 
   RawClass* At(intptr_t index) const {
     ASSERT(IsValidIndex(index));
     return table_[index];
   }
 
   intptr_t IsValidIndex(intptr_t index) const {
     return (index > 0) && (index < top_);
   }
 
   void Register(const Class& cls);
 
   void VisitObjectPointers(ObjectPointerVisitor* visitor);
 
   void Print();
 
+  static intptr_t table_offset() {
+    return OFFSET_OF(ClassTable, table_);
+  }
+
  private:
   static const int initial_capacity_ = 512;
   static const int capacity_increment_ = 256;
 
   intptr_t top_;
   intptr_t capacity_;
 
   RawClass** table_;
 
   DISALLOW_COPY_AND_ASSIGN(ClassTable);
 };
 
 }  // namespace dart
 
 #endif  // VM_CLASS_TABLE_H_