Those were popups from whatever website you went to. You can just keep pressing the back button, close out the window and chrome. No need to download anything.
I see those kinds of popups...erm...I mean my friend told me he sees those kinds of bogus virus/security alerts when he watches porn on his phone.
My advice would be to not click on anything you see. Not even an "ok" to dismiss something. If you can't back-button out of that mess, hit home to get out and force close your browser.
Since it was new to me, I posted right away. an FYI post.