Make assertion scopes thread safe.

src/ia32/assembler-ia32.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 393 matching lines @@
   }
 
   static Operand StaticArray(Register index,
                              ScaleFactor scale,
                              const ExternalReference& arr) {
     return Operand(index, scale, reinterpret_cast<int32_t>(arr.address()),
                    RelocInfo::EXTERNAL_REFERENCE);
   }
 
   static Operand Cell(Handle<JSGlobalPropertyCell> cell) {
-    ALLOW_HANDLE_DEREF(Isolate::Current(), "embedding raw address");
+    AllowDeferredHandleDereference embedding_raw_address;
     return Operand(reinterpret_cast<int32_t>(cell.location()),
                    RelocInfo::GLOBAL_PROPERTY_CELL);
   }
 
   // Returns true if this Operand is a wrapper for the specified register.
   bool is_reg(Register reg) const;
 
   // Returns true if this Operand is a wrapper for one register.
   bool is_reg_only() const;
 
@@ skipping 794 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_ASSEMBLER_IA32_H_