Support embed_domain for javascript events

[terrysmith-fiworks]

Please add support for the embed_domain which is required for catching javascript events.

[dthorpe]

Hi Terry,

Have you added your host page domain name to the embed domain whitelist on the Admin/Embed page?

-Danny

[terrysmith-fiworks]

Yes, I have. I know I'm not the only one having trouble because several people on this page have commented about it not not working with SSO iFrames:
https://discourse.looker.com/t/javascript-embedded-iframe-events/2298
I'm not positive on this and have tried it different ways, but I think the problem with the C# code is that it's using Path on the UriBuilder (where the embed_domain seems to go) for both the string that's encoded and for constructing the final path with builder.Uri.