Chrome Version       : 51.0.2704.63 (Official Build) (64-bit)
OS                   : Linux

Situation:
When trying to unmask a downstreamed card, the "Verify your Visa" or similar dialog appears for you to enter your CVC.

Problem 1:
The following things will NOT cause the dialog to go away:
1) Using the Back or Forward browser buttons
2) Refreshing the page
3) Using the URL bar to navigate to other pages on the same domain (like going from https://dump-truck.appspot.com/usecase-address_and_cc_on_same_page/address_and_cc.html to https://dump-truck.appspot.com/ to https://dump-truck.appspot.com/usecase-address_then_cc/address.html)

Note that as long as the dialog is live, the rest of the page is unusable.

Problem 2 (likely unimportant as long as Problem 1 is fixed):
Navigating to a new page and then entering a CVC and clicking verify causes the "Verifying card..." message to stick around forever, instead of timing out.