Move platform_thread to base/threading and put in the base namespace. I left ...

base/platform_thread_mac.mm

-// Copyright (c) 2006-2008 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.
-
-#include "base/platform_thread.h"
-
-#import <Foundation/Foundation.h>
-#include <dlfcn.h>
-
-#include "base/logging.h"
-
-namespace base {
-
-// If Cocoa is to be used on more than one thread, it must know that the
-// application is multithreaded.  Since it's possible to enter Cocoa code
-// from threads created by pthread_thread_create, Cocoa won't necessarily
-// be aware that the application is multithreaded.  Spawning an NSThread is
-// enough to get Cocoa to set up for multithreaded operation, so this is done
-// if necessary before pthread_thread_create spawns any threads.
-//
-// http://developer.apple.com/documentation/Cocoa/Conceptual/Multithreading/CreatingThreads/chapter_4_section_4.html
-void InitThreading() {
-  static BOOL multithreaded = [NSThread isMultiThreaded];
-  if (!multithreaded) {
-    // +[NSObject class] is idempotent.
-    [NSThread detachNewThreadSelector:@selector(class)
-                             toTarget:[NSObject class]
-                           withObject:nil];
-    multithreaded = YES;
-
-    DCHECK([NSThread isMultiThreaded]);
-  }
-}
-
-}  // namespace base
-
-// static
-void PlatformThread::SetName(const char* name) {
-  // pthread_setname_np is only available in 10.6 or later, so test
-  // for it at runtime.
-  int (*dynamic_pthread_setname_np)(const char*);
-  *reinterpret_cast<void**>(&dynamic_pthread_setname_np) =
-      dlsym(RTLD_DEFAULT, "pthread_setname_np");
-  if (!dynamic_pthread_setname_np)
-    return;
-
-  // Mac OS X does not expose the length limit of the name, so
-  // hardcode it.
-  const int kMaxNameLength = 63;
-  std::string shortened_name = std::string(name).substr(0, kMaxNameLength);
-  // pthread_setname() fails (harmlessly) in the sandbox, ignore when it does.
-  // See http://crbug.com/47058
-  dynamic_pthread_setname_np(shortened_name.c_str());
-}