have discovered one example where 'retry with patch' failed to catch a flake, but a full CQ retry caught it:

https://chromium-cq-status.appspot.com/v2/patch-status/chromium-review.googlesource.com/1229737/5

https://ci.chromium.org/p/chromium/builders/luci.chromium.try/win7_chromium_rel_ng/88226

It looks like the test "virtual/threaded/fast/events/touch/gesture/touch-gesture-scroll-page-zoomed.html" flaked both the original 'with patch' run, and the 'retry with patch' run.

1) This test "virtual/threaded/fast/events/touch/gesture/touch-gesture-scroll-page-zoomed.html" flakes.
2) It's retried three times at the end of the test suite. It fails all three times.
3) We roll checkout, rebuild, and then test again. It fails once [no retries].

So I tried running it locally. Exact same results. Same failure.

"""
C:\src\chromium\src>.\out\gn\content_shell.exe --run-web-tests --no-sandbox --enable-threaded-compositing C:\src\chromium\src\third_party\WebKit\LayoutTests\fast\events\touch\gesture\touch-gesture-scroll-page-zoomed.html

C:\src\chromium\src>#READY

DevTools listening on ws://127.0.0.1:56880/devtools/browser/18e55026-38fb-461c-aa45-2028861f006d
Content-Type: text/plain
This is a testharness.js-based test.
FAIL This tests scroll gesture event scrolling on a whole page with browserzoom. promise_test: Unhandled rejection with value: "Reaches the maximum frames."
Harness: the test ran to completion.

#EOF
#EOF
#EOF
[10824:21340:0919/094215.367:WARNING:discardable_shared_memory_manager.cc(438)] Some MojoDiscardableSharedMemoryManagerImpls are still alive. They will be leaked.
"""

This passes when I don't pass "--enable-threaded-compositing"

"""
C:\src\chromium\src>.\out\gn\content_shell.exe --run-web-tests --no-sandbox C:\src\chromium\src\third_party\WebKit\LayoutTests\fast\events\touch\gesture\touch-gesture-scroll-page-zoomed.html

C:\src\chromium\src>#READY

DevTools listening on ws://127.0.0.1:57003/devtools/browser/8ef61312-100b-463a-8e73-c9d5708b7519
Content-Type: text/plain
This is a testharness.js-based test.
PASS This tests scroll gesture event scrolling on a whole page with browserzoom.
Harness: the test ran to completion.

#EOF
#EOF
#EOF
[6280:14008:0919/094506.682:WARNING:discardable_shared_memory_manager.cc(438)] Some MojoDiscardableSharedMemoryManagerImpls are still alive. They will be leaked.
"""