Remove #pragma once. Just from base/ for now.

base/threading/worker_pool_posix.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.
 //
 // The thread pool used in the POSIX implementation of WorkerPool dynamically
 // adds threads as necessary to handle all tasks.  It keeps old threads around
 // for a period of time to allow them to be reused.  After this waiting period,
 // the threads exit.  This thread pool uses non-joinable threads, therefore
 // worker threads are not joined during process shutdown.  This means that
 // potentially long running tasks (such as DNS lookup) do not block process
 // shutdown, but also means that process shutdown may "leak" objects.  Note that
 // although PosixDynamicThreadPool spawns the worker threads and manages the
 // task queue, it does not own the worker threads.  The worker threads ask the
 // PosixDynamicThreadPool for work and eventually clean themselves up.  The
 // worker threads all maintain scoped_refptrs to the PosixDynamicThreadPool
 // instance, which prevents PosixDynamicThreadPool from disappearing before all
 // worker threads exit.  The owner of PosixDynamicThreadPool should likewise
 // maintain a scoped_refptr to the PosixDynamicThreadPool instance.
 //
 // NOTE: The classes defined in this file are only meant for use by the POSIX
 // implementation of WorkerPool.  No one else should be using these classes.
 // These symbols are exported in a header purely for testing purposes.
 
 #ifndef BASE_THREADING_WORKER_POOL_POSIX_H_
 #define BASE_THREADING_WORKER_POOL_POSIX_H_
-#pragma once
 
 #include <queue>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/location.h"
 #include "base/time.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 54 matching lines @@
   // Only used for tests to ensure correct thread ordering.  It will always be
   // NULL in non-test code.
   scoped_ptr<ConditionVariable> num_idle_threads_cv_;
 
   DISALLOW_COPY_AND_ASSIGN(PosixDynamicThreadPool);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_WORKER_POOL_POSIX_H_