FBTF: Remove unneeded headers from base/ (part 9)

base/singleton.h

 // Copyright (c) 2010 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 BASE_SINGLETON_H_
 #define BASE_SINGLETON_H_
 #pragma once
 
 #include "base/at_exit.h"
 #include "base/atomicops.h"
+#include "base/platform_thread.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 
 // Default traits for Singleton<Type>. Calls operator new and operator delete on
 // the object. Registers automatic deletion at process exit.
 // Overload if you need arguments or another memory allocation function.
 template<typename Type>
 struct DefaultSingletonTraits {
   // Allocates the object.
   static Type* New() {
     // The parenthesis is very important here; it forces POD type
@@ skipping 228 matching lines @@
     instance_ = 0;
   }
   static base::subtle::AtomicWord instance_;
 };
 
 template <typename Type, typename Traits, typename DifferentiatingType>
 base::subtle::AtomicWord Singleton<Type, Traits, DifferentiatingType>::
     instance_ = 0;
 
 #endif  // BASE_SINGLETON_H_