iframe in dialog reloads on dialog focus loss

How to reproduce:

In Firefox or Chrome (tested with 26.0.1410.43), open this jsbin: http://jsbin.com/uzazod/2/edit

Click the button twice.

Move the dialogs to be able to see both iframes

click both dialogs alternately and watch the iframe from the now passive dialog. The iframe reloads its contents.

Expected behaviour: Open this jsbin: http://jsbin.com/uzazod/3/

Repeat the steps and notice how the iframe is not reloading.