Bug 1911977 - Don't abort networking activity on external protocol navigations. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D221029

docshell/base/nsDocShell.cpp

@@ -9271,6 +9271,8 @@ nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
   // XXXbz mTiming should know what channel it's for, so we don't
   // need this hackery.
   const bool isJavaScript = SchemeIsJavascript(aLoadState->URI());
+  const bool isExternalProtocol =
+      nsContentUtils::IsExternalProtocol(aLoadState->URI());
   const bool isDownload = !aLoadState->FileName().IsVoid();
   const bool toBeReset = !isJavaScript && MaybeInitTiming();
 
@@ -9281,6 +9283,9 @@ nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
   }
   // Check if the page doesn't want to be unloaded. The javascript:
   // protocol handler deals with this for javascript: URLs.
+  // NOTE(emilio): As of this writing, other browsers fire beforeunload for
+  // external protocols, so keep doing that even though they don't return data
+  // and thus we won't really unload this...
   if (!isJavaScript && !isDownload &&
       !aLoadState->NotifiedBeforeUnloadListeners() && mDocumentViewer) {
     // Check if request is exempted from HTTPSOnlyMode and if https-first is
@@ -9380,7 +9385,7 @@ nsresult nsDocShell::InternalLoad(nsDocShellLoadState* aLoadState,
   // In the case where they do result in data, the javascript: URL channel takes
   // care of stopping current network activity. Similarly, downloads don't
   // unload this document...
-  if (!isJavaScript && !isDownload) {
+  if (!isJavaScript && !isDownload && !isExternalProtocol) {
     // Stop any current network activity.
     // Also stop content if this is a zombie doc. otherwise
     // the onload will be delayed by other loads initiated in the

dom/base/test/file_location_href_unknown_protocol.html

@@ -3,8 +3,11 @@
 onbeforeunload = function() {
   opener.onChildBeforeUnload();
 };
-onload = function() {
+onload = async function() {
+  let ongoingLoad = fetch(location.href);
   location.href = "this-protocol-is-unlikely-to-exist://foo";
+  // Load shouldn't be canceled.
+  await ongoingLoad;
   setTimeout(function() {
     opener.onChildLoadTimedOut();
   }, 1000);