Remove unused field.

BUG=

Review URL: https://chromiumcodereview.appspot.com/12789004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13930 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/optimizing-compiler-thread.h

@@ -93,7 +93,6 @@ class OptimizingCompilerThread : public Thread {
   Isolate* isolate_;
   Semaphore* stop_semaphore_;
   Semaphore* input_queue_semaphore_;
-  Semaphore* output_queue_semaphore_;
   UnboundQueue<OptimizingCompiler*> input_queue_;
   UnboundQueue<OptimizingCompiler*> output_queue_;
   volatile AtomicWord stop_thread_;