Chrome Version: 57.0.2971.0
OS: Win10

What steps will reproduce the problem?
(0) Enable "Auto-attach to cross-process subframes" DevTools experiment and start Chrome with --site-per-process (see  https://crbug.com/652783#c8 ).
(1) Visit http://csreis.github.io/tests/cross-site-iframe-simple.html
(2) Right click on main frame and choose Inspect.
(3) In the Audits tab, click Run.

What is the expected result?
The audit should complete and show results (e.g., Leverage browser caching and Remove unused CSS rules).

What happens instead?
The progress bar next to "Running audit" never finishes, and the Audits tab is left mostly unresponsive.