Oilpan: make DOMWindowProperty a GC mixin.

Source/modules/netinfo/NavigatorNetworkInformation.cpp

Index: Source/modules/netinfo/NavigatorNetworkInformation.cpp
diff --git a/Source/modules/netinfo/NavigatorNetworkInformation.cpp b/Source/modules/netinfo/NavigatorNetworkInformation.cpp
index 7331e416490830916ef72547144c8e1c1a42063b..a1fea71d68a621730dfc7e1f48a88883dcb0ad63 100644
--- a/Source/modules/netinfo/NavigatorNetworkInformation.cpp
+++ b/Source/modules/netinfo/NavigatorNetworkInformation.cpp
@@ -17,9 +17,7 @@ NavigatorNetworkInformation::NavigatorNetworkInformation(Navigator& navigator)
 {
 }
 
-NavigatorNetworkInformation::~NavigatorNetworkInformation()
-{
-}
+DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(NavigatorNetworkInformation);
 
 NavigatorNetworkInformation& NavigatorNetworkInformation::from(Navigator& navigator)
 {
@@ -59,6 +57,7 @@ void NavigatorNetworkInformation::trace(Visitor* visitor)
 {
     visitor->trace(m_connection);
     WillBeHeapSupplement<Navigator>::trace(visitor);
+    DOMWindowProperty::trace(visitor);
 }
 
 } // namespace blink