Make assertion scopes thread safe.

src/arm/macro-assembler-arm.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 144 matching lines @@
                 Heap::RootListIndex index,
                 Condition cond = al);
   // Store an object to the root table.
   void StoreRoot(Register source,
                  Heap::RootListIndex index,
                  Condition cond = al);
 
   void LoadHeapObject(Register dst, 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 {
       Move(result, object);
     }
   }
 
   // ---------------------------------------------------------------------------
   // GC Support
 
@@ skipping 1270 matching lines @@
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_MACRO_ASSEMBLER_ARM_H_