These three interfaces were missing from the global scope entirely.
Site bundles that reference Plugin as a constructor threw
"ReferenceError: Plugin is not defined".
Added as plain function declarations (same pattern as PluginArray) so
they survive the V8 snapshot. navigator.plugins now returns real Plugin
instances and navigator.mimeTypes returns a real MimeTypeArray with
MimeType instances, so instanceof checks work correctly.
Gabriel
a8358cc82d