Simplify implementation of Mutex.

src/platform-nullos.cc

 // 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 459 matching lines @@
 void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
   UNIMPLEMENTED();
 }
 
 
 void Thread::YieldCPU() {
   UNIMPLEMENTED();
 }
 
 
-class NullMutex : public Mutex {
- public:
-  NullMutex() : data_(NULL) {
-    UNIMPLEMENTED();
-  }
-
-  virtual ~NullMutex() {
-    UNIMPLEMENTED();
-  }
-
-  virtual int Lock() {
-    UNIMPLEMENTED();
-    return 0;
-  }
-
-  virtual int Unlock() {
-    UNIMPLEMENTED();
-    return 0;
-  }
-
- private:
-  void* data_;
-};
-
-
-Mutex* OS::CreateMutex() {
-  UNIMPLEMENTED();
-  return new NullMutex();
-}
-
-
 class NullSemaphore : public Semaphore {
  public:
   explicit NullSemaphore(int count) : data_(NULL) {
     UNIMPLEMENTED();
   }
 
   virtual ~NullSemaphore() {
     UNIMPLEMENTED();
   }
 
@@ skipping 43 matching lines @@
   UNIMPLEMENTED();
 }
 
 
 void ProfileSampler::Stop() {
   UNIMPLEMENTED();
 }
 
 
 } }  // namespace v8::internal