Improve scoped_cftyperef<> and scoped_nsobject<> reset() semantics.

base/scoped_nsobject.h

 // Copyright (c) 2009 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_SCOPED_NSOBJECT_H_
 #define BASE_SCOPED_NSOBJECT_H_
 
 #import <Foundation/Foundation.h>
 #include "base/basictypes.h"
 
 // scoped_nsobject<> is patterned after scoped_ptr<>, but maintains ownership
 // of an NSObject subclass object.  Style deviations here are solely for
 // compatibility with scoped_ptr<>'s interface, with which everyone is already
 // familiar.
 //
 // When scoped_nsobject<> takes ownership of an object (in the constructor or
 // in reset()), it takes over the caller's existing ownership claim.  The
-// caller must own the object.  scoped_nsobject<> does not call -retain.
+// caller must own the object it gives to scoped_nsobject<>, and relinquishes
+// an ownership claim to that object.  scoped_nsobject<> does not call
+// -retain.
 template<typename NST>
 class scoped_nsobject {
  public:
   typedef NST* element_type;
 
   explicit scoped_nsobject(NST* object = nil)
       : object_(object) {
   }
 
   ~scoped_nsobject() {
     [object_ release];
   }
 
   void reset(NST* object = nil) {
-    if (object_ != object) {
-      [object_ release];
-      object_ = object;
-    }
+    [object_ release];
+    object_ = object;
   }
 
   bool operator==(NST* that) const {
     return object_ == that;
   }
 
   bool operator!=(NST* that) const {
     return object_ != that;
   }
 
@@ skipping 20 matching lines @@
     return temp;
   }
 
  private:
   NST* object_;
 
   DISALLOW_COPY_AND_ASSIGN(scoped_nsobject);
 };
 
 #endif  // BASE_SCOPED_NSOBJECT_H_