Bug 1551344 - Part 2: Update outdated comments referencing XULDocument. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D41239

caps/nsScriptSecurityManager.cpp

@@ -362,7 +362,7 @@ nsScriptSecurityManager::GetChannelURIPrincipal(nsIChannel* aChannel,
   MOZ_ASSERT(aChannel, "Must have channel!");
 
   // Get the principal from the URI.  Make sure this does the same thing
-  // as Document::Reset and XULDocument::StartDocumentLoad.
+  // as Document::Reset and PrototypeDocumentContentSink::Init.
   nsCOMPtr<nsIURI> uri;
   nsresult rv = NS_GetFinalChannelURI(aChannel, getter_AddRefs(uri));
   NS_ENSURE_SUCCESS(rv, rv);