DCHECK when an ObjCPropertyReleaser has no properties to release.

base/mac/objc_property_releaser.mm

 // 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.
 
 #import "base/mac/objc_property_releaser.h"
 
 #import <objc/runtime.h>
 #include <stdlib.h>
 
 #include <string>
@@ skipping 86 matching lines @@
   class_ = classy;
 }
 
 void ObjCPropertyReleaser::ReleaseProperties() {
   DCHECK(object_);
   DCHECK(class_);
 
   unsigned int property_count = 0;
   objc_property_t* properties = class_copyPropertyList(class_, &property_count);
 
+  bool released_something = false;
   for (unsigned int property_index = 0;
        property_index < property_count;
        ++property_index) {
     objc_property_t property = properties[property_index];
     std::string instance_name = ReleasableInstanceName(property);
     if (!instance_name.empty()) {
       id instance_value = nil;
       Ivar instance_variable =
           object_getInstanceVariable(object_, instance_name.c_str(),
                                      (void**)&instance_value);
       DCHECK(instance_variable);
       [instance_value release];
+      released_something = true;
     }
   }
 
+  // Check that this property releaser was of some use.
+  DCHECK(released_something);
+
   free(properties);
 
   // Clear object_ and class_ in case this ObjCPropertyReleaser will live on.
   // It's only expected to release the properties it supervises once per Init.
   object_ = nil;
   class_ = nil;
 }
 
 }  // namespace mac
 }  // namespace base