This would seem to be a regression. I just tried it (Linux 54.0.2840.71) and it seems to work fine for me. Can you do a bisect?

Just tested on ToT with --enable-features=GuestViewCrossProcessFrames --site-per-process

https://null.badssl.com/ shows an error page correctly. (ERR_SSL_VERSION_OR_CIPHER_MISMATCH)

https://untrusted-root.badssl.com/ and 
https://revoked.badssl.com/ seem to fail.

The spinner in browser sample sometimes stops spinning without the page changing. You can click other links in the original page (badssl.com lists all the tests cases).

For example: click revoked then once the spinner stops, click hsts (which should work). The url bar does update to hsts.badssl.com but nothing happens.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1453e416f1a511576ff3ee6641e6a77a651b2ef4

commit 1453e416f1a511576ff3ee6641e6a77a651b2ef4
Author: lfg <lfg@chromium.org>
Date: Tue Apr 11 00:48:50 2017

Fix interstitials on OOPIF-based guests.

This CL attaches the interstitial RenderWidgetHostViewChildFrame to a
CrossProcessFrameConnector in a RenderFrameProxyHost in an outer
WebContents when an interstitial page gets attached. It also routes
input events in the interstitial through the delegate's WebContents
RenderWidgetHostInputEventRouter.

BUG= 660373 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2797473005
Cr-Commit-Position: refs/heads/master@{#463473}

[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/chrome/browser/apps/guest_view/web_view_browsertest.cc
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/chrome/test/data/extensions/platform_apps/web_view/interstitial_teardown/embedder.js
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/chrome/test/data/extensions/platform_apps/web_view/interstitial_teardown/main.html
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/browser/frame_host/interstitial_page_impl.cc
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/browser/frame_host/interstitial_page_impl.h
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/browser/frame_host/render_widget_host_view_child_frame.cc
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/browser/renderer_host/render_widget_host_input_event_router.cc
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/browser/renderer_host/render_widget_host_input_event_router.h
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/browser/web_contents/web_contents_impl.cc
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/browser/web_contents/web_contents_impl.h
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/public/test/browser_test_utils.cc
[modify] https://crrev.com/1453e416f1a511576ff3ee6641e6a77a651b2ef4/content/public/test/browser_test_utils.h