Bug 1375386 - Silence a -Wunused-lambda-capture warning r=froydnj

MozReview-Commit-ID: CoIXICb4nwY

--HG--
extra : rebase_source : 47ab8f3f20243abc778402e4aba13969c83c1b8e

dom/workers/RuntimeService.cpp

@@ -1649,6 +1649,7 @@ RuntimeService::RegisterWorker(WorkerPrivate* aWorkerPrivate)
     domainInfo = mDomainMap.LookupForAdd(domain).OrInsert(
       [&domain, parent] () {
         NS_ASSERTION(!parent, "Shouldn't have a parent here!");
+        Unused << parent; // silence clang -Wunused-lambda-capture in opt builds
         WorkerDomainInfo* wdi = new WorkerDomainInfo();
         wdi->mDomain = domain;
         return wdi;