Add ScopedObjCClassSwizzler in base/mac, absorbs objc_method_swizzle and ScopedClassSwizzler

chrome/common/mac/objc_method_swizzle.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.
-
-#ifndef CHROME_COMMON_MAC_OBJC_METHOD_SWIZZLE_H_
-#define CHROME_COMMON_MAC_OBJC_METHOD_SWIZZLE_H_
-
-#import <objc/runtime.h>
-
-// You should think twice every single time you use anything from this
-// namespace.
-namespace ObjcEvilDoers {
-
-// This is similar to class_getInstanceMethod(), except that it
-// returns NULL if |aClass| does not directly implement |aSelector|.
-Method GetImplementedInstanceMethod(Class aClass, SEL aSelector);
-
-// Exchanges the implementation of |originalSelector| and
-// |alternateSelector| within |aClass|.  Both selectors must be
-// implemented directly by |aClass|, not inherited.  The IMP returned
-// is for |originalSelector| (for purposes of forwarding).
-IMP SwizzleImplementedInstanceMethods(
-    Class aClass, const SEL originalSelector, const SEL alternateSelector);
-
-}  // namespace ObjcEvilDoers
-
-#endif  // CHROME_COMMON_MAC_OBJC_METHOD_SWIZZLE_H_