[NaCl SDK] Add nacl_mounts to NaCl SDK build. Experimental for now.

native_client_sdk/src/libraries/utils/auto_lock.h

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef LIBRARIES_UTILS_AUTO_LOCK_H_
 #define LIBRARIES_UTILS_AUTO_LOCK_H_
 
 #include <pthread.h>
 
 class AutoLock {
  public:
   explicit AutoLock(pthread_mutex_t* lock) {
     lock_ = lock;
     pthread_mutex_lock(lock_);
   }
   ~AutoLock() {
     if (lock_) pthread_mutex_unlock(lock_);
   }
 
+  void Unlock() {
+    if (lock_) pthread_mutex_unlock(lock_);
+    lock_ = NULL;
+  }
+
  private:
   pthread_mutex_t* lock_;
 };
 
 #endif  // LIBRARIES_UTILS_AUTO_LOCK_H_