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

base/scoped_cftyperef.h

 // 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.
 
 #ifndef BASE_SCOPED_CFTYPEREF_H_
 #define BASE_SCOPED_CFTYPEREF_H_
 
 #include <CoreFoundation/CoreFoundation.h>
 #include "base/basictypes.h"
 
 // scoped_cftyperef<> is patterned after scoped_ptr<>, but maintains ownership
 // of a CoreFoundation object: any object that can be represented as a
 // CFTypeRef.  Style deviations here are solely for compatibility with
 // scoped_ptr<>'s interface, with which everyone is already familiar.
 //
 // When scoped_cftyperef<> 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_cftyperef<> does not call CFRetain().
+// caller must own the object it gives to scoped_cftyperef<>, and relinquishes
+// an ownership claim to that object.  scoped_cftyperef<> does not call
+// CFRetain().
 template<typename CFT>
 class scoped_cftyperef {
  public:
   typedef CFT element_type;
 
   explicit scoped_cftyperef(CFT object = NULL)
       : object_(object) {
   }
 
   ~scoped_cftyperef() {
     if (object_)
       CFRelease(object_);
   }
 
   void reset(CFT object = NULL) {
-    if (object_ != object) {
-      if (object_)
-        CFRelease(object_);
-      object_ = object;
-    }
+    if (object_)

[TVL, 2009/03/23 17:30:22]

part of me thinks it's better to match the other scoped_* helpers so they are
all alike.  the downside, here is w/o the equality check, if someone updated
this w/o checking for equality, it could store a stale pointer since it will
dump the object and then keep the ptr again.

+      CFRelease(object_);
+    object_ = object;
   }
 
   bool operator==(CFT that) const {
     return object_ == that;
   }
 
   bool operator!=(CFT that) const {
     return object_ != that;
   }
 
@@ skipping 20 matching lines @@
     return temp;
   }
 
  private:
   CFT object_;
 
   DISALLOW_COPY_AND_ASSIGN(scoped_cftyperef);
 };
 
 #endif  // BASE_SCOPED_CFTYPEREF_H_