Make assertion scopes thread safe.

src/ia32/macro-assembler-ia32.h

 // Copyright 2012 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 258 matching lines @@
   // register stack slot for register dst.
   void StoreToSafepointRegisterSlot(Register dst, Register src);
   void StoreToSafepointRegisterSlot(Register dst, Immediate src);
   void LoadFromSafepointRegisterSlot(Register dst, Register src);
 
   void LoadHeapObject(Register result, Handle<HeapObject> object);
   void CmpHeapObject(Register reg, Handle<HeapObject> object);
   void PushHeapObject(Handle<HeapObject> object);
 
   void LoadObject(Register result, Handle<Object> object) {
-    ALLOW_HANDLE_DEREF(isolate(), "heap object check");
+    AllowDeferredHandleDereference heap_object_check;
     if (object->IsHeapObject()) {
       LoadHeapObject(result, Handle<HeapObject>::cast(object));
     } else {
       Set(result, Immediate(object));
     }
   }
 
   void CmpObject(Register reg, Handle<Object> object) {
-    ALLOW_HANDLE_DEREF(isolate(), "heap object check");
+    AllowDeferredHandleDereference heap_object_check;
     if (object->IsHeapObject()) {
       CmpHeapObject(reg, Handle<HeapObject>::cast(object));
     } else {
       cmp(reg, Immediate(object));
     }
   }
 
   // ---------------------------------------------------------------------------
   // JavaScript invokes
 
@@ skipping 743 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_MACRO_ASSEMBLER_IA32_H_