[ISSUE-19208] If scaladocs on file protocol don't do SPA routing.

If we detect scaladocs are being served locally
(i.e page on the "file" protocol)
then we let the link click event go back to normal handling.

Otherwise unless a user has allowed pages on the file protocol
to access other files
https://github.com/chromium/chromium/blob/b6c23ba2056e65081f8a5bcbf73b176baaa42645/content/public/common/content_switches.cc#L15
for example with the allow-file-access-from-files flag in chrome
then SPA routing won't work.

Author: Math-ias

scaladoc/resources/dotty_res/scripts/ux.js

@@ -167,6 +167,11 @@ function attachAllListeners() {
       if (url.origin !== window.location.origin) {
         return;
       }
+      // ISSUE-19208, treat as normal link when lacking HTTP server,
+      // otherwise GET request blocked by CORS protections.
+      if (window.location.protocol.startsWith("file")) {
+        return;
+      }
       if (e.metaKey || e.ctrlKey || e.shiftKey || e.altKey || e.button !== 0) {
         return;
       }