In issue 786505 , we added logic to block cross-site documents from renderer processes when Site Isolation modes are enabled. This helps prevent sensitive information from leaking to a process that doesn't need access to it.
There are still many cross-site network responses that do need to be delivered to the renderer (e.g., scripts, images, stylesheets, etc). We make an effort not to block anything that could be disruptive, but there may still be cases that affect a page's execution, especially if content is not labeled with the correct MIME type.
It would be helpful to web developers to have a console message when a blocking event occurs. pfeldman@ noted there may be a good way to plumb that information along with the response.
I'm adding a very simple first draft of a message in https://chromium-review.googlesource.com/c/chromium/src/+/817661 which is only displayed for script tags. We should replace that with a more consistent message if possible.
Comment 1 by creis@chromium.org
, Dec 12 2017