Causing a text diff. Could be due to site-per-process (as indicated by FindIt).

--- /b/s/w/ioZlc5o8/layout-test-results/http/tests/inspector-protocol/network/navigation-blocking-xorigin-iframe-expected.txt
+++ /b/s/w/ioZlc5o8/layout-test-results/http/tests/inspector-protocol/network/navigation-blocking-xorigin-iframe-actual.txt
@@ -3,14 +3,13 @@
 [
     [0] : http://127.0.0.1:8000/inspector-protocol/resources/iframe-navigation.html
     [1] : http://devtools.oopif-a.test:8000/inspector-protocol/resources/meta-tag.html
-    [2] : http://devtools.oopif-a.test:8000/inspector-protocol/resources/test-page.html
-    [3] : http://devtools.oopif-b.test:8000/inspector-protocol/resources/meta-tag.html
-    [4] : http://devtools.oopif-b.test:8000/inspector-protocol/resources/test-page.html: Aborted
+    [2] : http://devtools.oopif-b.test:8000/inspector-protocol/resources/meta-tag.html
+    [3] : http://devtools.oopif-b.test:8000/inspector-protocol/resources/test-page.html: Aborted
 ]
 Frames in page:
 [
     [0] : http://127.0.0.1:8000/inspector-protocol/resources/iframe-navigation.html
-    [1] : http://devtools.oopif-a.test:8000/inspector-protocol/resources/test-page.html
+    [1] : http://devtools.oopif-a.test:8000/inspector-protocol/resources/meta-tag.html
     [2] : http://devtools.oopif-b.test:8000/inspector-protocol/resources/meta-tag.html
 ]
 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d9f62a2e64871f4a2275f2f39abc61aa33995607

commit d9f62a2e64871f4a2275f2f39abc61aa33995607
Author: Yuta Kitamura <yutak@chromium.org>
Date: Tue Nov 20 06:59:07 2018

Update layout test expectations.

Bug: 906952, 906879 
Change-Id: I0c7bec172a28b37c8b8c3c8e33c7e2f1630d8404
Tbr: kolos@chromium.org
Tbr: pavely@chromium.org
Tbr: hongjunchoi@chromium.org
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/1343475
Reviewed-by: Yuta Kitamura <yutak@chromium.org>
Commit-Queue: Yuta Kitamura <yutak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609616}
[modify] https://crrev.com/d9f62a2e64871f4a2275f2f39abc61aa33995607/third_party/WebKit/LayoutTests/TestExpectations

Not bleeding anymore, down to P2.

I can repro on Linux - 17 out of 20 runs fail at r609486.  No failures with --additional-driver-flag=--disable-site-isolation-trials.

I can restore test coverage via virtual/not-site-per-process.  I'll put together a CL to do that in a minute.

I think I'll need help from DevTools devs with fixing the test - I am guessing that |await loadPromise| is not sufficient to get into a stable/testable/verifiable state.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/27a0372562de554946280cc45f7930623aeea27d

commit 27a0372562de554946280cc45f7930623aeea27d
Author: Lukasz Anforowicz <lukasza@chromium.org>
Date: Tue Nov 20 19:57:07 2018

Move test expectations for navigation-blocking-xorigin-iframe.js

This CL associates test expectations for navigation-blocking-xorigin-iframe.js
with Site Isolation, and restores test coverage offerred by this test
(via virtual/not-site-per-process test suite).

Bug:  906879 
Change-Id: If57837cf0650f02c4ce58665d845462c4422cce5
Reviewed-on: https://chromium-review.googlesource.com/c/1344258
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609780}
[modify] https://crrev.com/27a0372562de554946280cc45f7930623aeea27d/third_party/WebKit/LayoutTests/TestExpectations
[modify] https://crrev.com/27a0372562de554946280cc45f7930623aeea27d/third_party/WebKit/LayoutTests/VirtualTestSuites

caseq@, could you PTAL at what makes the test flaky in presence of OOPIFs?  (I think you've introduced the test in r555924).

Test failures are processed as a part of a dedicated triage, bulk-closing the bugs.