Make assertion scopes thread safe.

src/api.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 618 matching lines @@
   spare_ = NULL;
   return block;
 }
 
 
 void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
   while (!blocks_.is_empty()) {
     internal::Object** block_start = blocks_.last();
     internal::Object** block_limit = block_start + kHandleBlockSize;
 #ifdef DEBUG
-    // NoHandleAllocation may make the prev_limit to point inside the block.
+    // RequireNewHandleScope may make the prev_limit to point inside the block.
     if (block_start <= prev_limit && prev_limit <= block_limit) {
 #ifdef ENABLE_EXTRA_CHECKS
       internal::HandleScope::ZapRange(prev_limit, block_limit);
 #endif
       break;
     }
 #else
     if (prev_limit == block_limit) break;
 #endif
 
@@ skipping 18 matching lines @@
     stress_type_ = stress_type;
   }
 
  private:
   static v8::Testing::StressType stress_type_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_API_H_