Add mutex when accessing concurrent recompilation output queue.

src/optimizing-compiler-thread.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 97 matching lines @@
 #endif
 
   Isolate* isolate_;
   Semaphore stop_semaphore_;
   Semaphore input_queue_semaphore_;
 
   // Queue of incoming recompilation tasks (including OSR).
   UnboundQueue<OptimizingCompiler*> input_queue_;
   // Queue of recompilation tasks ready to be installed (excluding OSR).
   UnboundQueue<OptimizingCompiler*> output_queue_;
-  // List of all OSR related recompilation tasks (both incoming and ready ones).
+  // List of recompilation tasks for OSR in the input queue.
   List<OptimizingCompiler*> osr_candidates_;
   // List of recompilation tasks ready for OSR.
   List<OptimizingCompiler*> ready_for_osr_;
 
   volatile AtomicWord stop_thread_;
   volatile Atomic32 queue_length_;
   TimeDelta time_spent_compiling_;
   TimeDelta time_spent_total_;
 
+  // TODO(yangguo): remove this once the memory leak has been figured out.
+  Mutex queue_mutex_;
   Mutex osr_list_mutex_;
   int osr_hits_;
   int osr_attempts_;
 
   static const int kReadyForOSRLimit = 4;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OPTIMIZING_COMPILER_THREAD_H_