Fix debug builds.

src/log.cc

 // Copyright 2009 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 1460 matching lines @@
           stream.Put(*p);
         }
       }
       SmartPointer<const char> expanded = stream.ToCString();
       Log::OpenFile(*expanded);
     } else {
       Log::OpenFile(FLAG_logfile);
     }
   }
 
-  ASSERT(VMState::current_state_ == NULL);  // NULL implies outermost external.
+  ASSERT(VMState::is_outermost_external());
 
   ticker_ = new Ticker(kSamplingIntervalMs);
 
   if (FLAG_sliding_state_window && sliding_state_window_ == NULL) {
     sliding_state_window_ = new SlidingStateWindow();
   }
 
   log_events_ = FLAG_compress_log ?
       kCompressedLogEventsNames : kLongLogEventsNames;
   if (FLAG_compress_log) {
@@ skipping 68 matching lines @@
   }
   // Otherwise, if the sliding state window computation has not been
   // started we do it now.
   if (sliding_state_window_ == NULL) {
     sliding_state_window_ = new SlidingStateWindow();
   }
 #endif
 }
 
 } }  // namespace v8::internal