DCHECK when an ObjCPropertyReleaser has no properties to release.

base/mac/objc_property_releaser.mm

Index: base/mac/objc_property_releaser.mm
diff --git a/base/mac/objc_property_releaser.mm b/base/mac/objc_property_releaser.mm
index f7ee88fbcc4dd0e4c8d7b7ce95d9030021042324..b156ddc64d1d49dc4044a8f5f5419d9e0fb437d8 100644
--- a/base/mac/objc_property_releaser.mm
+++ b/base/mac/objc_property_releaser.mm
@@ -104,6 +104,7 @@ void ObjCPropertyReleaser::ReleaseProperties() {
   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) {
@@ -116,9 +117,13 @@ void ObjCPropertyReleaser::ReleaseProperties() {
                                      (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.