Remove unused base/memory/singleton_objc.h

base/memory/singleton_objc.h

-// Copyright (c) 2011 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.
-
-// Support for using the Singleton<T> pattern with Objective-C objects.  A
-// SingletonObjC is the same as a Singleton, except the default traits are
-// appropriate for Objective-C objects.  A typical Objective-C object of type
-// NSExampleType can be maintained as a singleton and accessed with:
-//
-//   NSExampleType* exampleSingleton = SingletonObjC<NSExampleType>::get();
-//
-// The first time this is used, it will create exampleSingleton as the result
-// of [[NSExampleType alloc] init].  Subsequent calls will return the same
-// NSExampleType* object.  The object will be released by calling
-// -[NSExampleType release] when Singleton's atexit routines run
-// (see singleton.h).
-//
-// For Objective-C objects initialized through means other than the
-// no-parameter -init selector, DefaultSingletonObjCTraits may be extended
-// as needed:
-//
-//   struct FooSingletonTraits : public DefaultSingletonObjCTraits<Foo> {
-//     static Foo* New() {
-//       return [[Foo alloc] initWithName:@"selecty"];
-//     }
-//   };
-//   ...
-//   Foo* widgetSingleton = SingletonObjC<Foo, FooSingletonTraits>::get();
-
-#ifndef BASE_MEMORY_SINGLETON_OBJC_H_
-#define BASE_MEMORY_SINGLETON_OBJC_H_
-
-#import <Foundation/Foundation.h>
-#include "base/memory/singleton.h"
-
-// Singleton traits usable to manage traditional Objective-C objects, which
-// are instantiated by sending |alloc| and |init| messages, and are deallocated
-// in a memory-managed environment when their retain counts drop to 0 by
-// sending |release| messages.
-template<typename Type>
-struct DefaultSingletonObjCTraits : public DefaultSingletonTraits<Type> {
-  static Type* New() {
-    return [[Type alloc] init];
-  }
-
-  static void Delete(Type* object) {
-    [object release];
-  }
-};
-
-// Exactly like Singleton, but without the DefaultSingletonObjCTraits as the
-// default trait class.  This makes it straightforward for Objective-C++ code
-// to hold Objective-C objects as singletons.
-template<typename Type,
-         typename Traits = DefaultSingletonObjCTraits<Type>,
-         typename DifferentiatingType = Type>
-class SingletonObjC : public Singleton<Type, Traits, DifferentiatingType> {
-};
-
-#endif  // BASE_MEMORY_SINGLETON_OBJC_H_