An empty MIME type doesn't match any plugin, no matter what they may claim....

webkit/glue/webframeloaderclient_impl.cc

Index: webkit/glue/webframeloaderclient_impl.cc
===================================================================
--- webkit/glue/webframeloaderclient_impl.cc	(revision 12907)
+++ webkit/glue/webframeloaderclient_impl.cc	(working copy)
@@ -1246,7 +1246,7 @@
   // See if the type is handled by an installed plugin, if so, we can show it.
   // TODO(beng): (http://b/1085524) This is the place to stick a preference to
   //             disable full page plugins (optionally for certain types!)
-  return plugin_data && plugin_data->supportsMimeType(mime_type);
+  return !mime_type.isEmpty() && plugin_data && plugin_data->supportsMimeType(mime_type);
 }
 
 bool WebFrameLoaderClient::representationExistsForURLScheme(const String& URLScheme) const {
@@ -1540,7 +1540,7 @@
 
   // If Chrome is started with the --disable-plugins switch, pluginData is null.
   PluginData* plugin_data = webframe_->frame()->page()->pluginData();
-  if (plugin_data && plugin_data->supportsMimeType(mime_type))
+  if (!mime_type.isEmpty() && plugin_data && plugin_data->supportsMimeType(mime_type))

[jam, 2009/04/02 20:31:34]

I believe this one isn't needed because of line 1527

[Pam (message me for reviews), 2009/04/02 20:34:07]

Right. Removed.

     return ObjectContentNetscapePlugin;
 
   if (MIMETypeRegistry::isSupportedNonImageMIMEType(mime_type))