Bug 1238723 - Tab child needs to use default user context id when handling permissions. r=sicking

dom/ipc/ContentChild.cpp

@@ -2492,6 +2492,10 @@ ContentChild::RecvAddPermission(const IPC::Permission& permission)
   nsAutoCString originNoSuffix;
   PrincipalOriginAttributes attrs;
   attrs.PopulateFromOrigin(permission.origin, originNoSuffix);
+  // we're doing this because we currently don't support isolating permissions
+  // by userContextId.
+  MOZ_ASSERT(attrs.mUserContextId == nsIScriptSecurityManager::DEFAULT_USER_CONTEXT_ID,
+      "permission user context should be set to default!");
 
   nsCOMPtr<nsIURI> uri;
   nsresult rv = NS_NewURI(getter_AddRefs(uri), originNoSuffix);