Version: 54.0.2797.0
OS: All

In --site-per-process mode, if an iframe redirects cross-site during a back/forward navigation that does not affect the main frame, we'll classify the iframe commit as NEW_SUBFRAME rather than AUTO_SUBFRAME, and it will incorrectly create a new navigation entry.

This was discovered during the fix for  issue 585194 .  I have a test for it in https://codereview.chromium.org/2136873002/ which will initially be disabled for --site-per-process, and we can enable it once the bug is fixed.

I think the bug is due to the transfer, which doesn't set the correct load type.  Interestingly it doesn't affect the case that the back/forward first tells the main frame to go back, and then a subframe redirects.  It only occurs if the redirect is cross-process.