Fix leak from fix for bug 305689 (Cache event queue service in nsContentUtils). r/sr=bz.

content/base/src/nsContentUtils.cpp

@@ -444,6 +444,7 @@ nsContentUtils::Shutdown()
   NS_IF_RELEASE(sIOService);
   NS_IF_RELEASE(sLineBreaker);
   NS_IF_RELEASE(sWordBreaker);
+  NS_IF_RELEASE(sEventQueueService);
 #ifdef MOZ_XTF
   NS_IF_RELEASE(sXTFService);
 #endif