Rightclicking (and double right clicking) doesn't bring up any means to loop for me.
Is it a Google Chrome thing? I'm on Firefox.
To bring up the menu, use shift + right click.
[source]You'll need a third-party extension to add the loop option to the menu, though.
Edit: I use
HTML5 Loop despite the fact it's not restartless. Just be sure to
download 1.1.0 and disable auto-updating, like
this review suggests.
There's one that
is restartless (specifically
this), but the option was added to the end of the menu, and I didn't like that.