In  issue 656752  we fixed blob/filesystem URL issues with chrome-extensions. However, it was during the time when PlzNavigate was still in development. One CL in particular didn't get landed - https://codereview.chromium.org/2870843003, leaving the ProcessManagerBrowserTest.NestedURLNavigationsToAppBlocked failing. Since PlzNavigate has shipped for a while now, we should revisit landing the CL and ensuring that this test passes succsesfully.