Hi, Can you please try with ChromeDriver 2.40 instead? That is the latest released version. Also please link to your sponge logs as well.

Sponge link: http://sponge/c0becfeb-95ad-47ee-855c-8056d1dbf391

I will try using the latest ChromeDriver version, I don't know how to change this but will ask in webdriver-users

I read the CEF code, and basically CEF does not currently support the functionality that ChromeDriver needs. I filed a bug against them here with a ton of details: https://bitbucket.org/chromiumembedded/cef/issues/2476/cef-does-not-support-remote-debugging-port

If you want a quick and dirty solution, you can write a wrapper script for CEF that gets passed as the binary in ChromeOptions. The script would do the following:

1. Parse --user-data-dir argument as DIR.
2. Pick a random free port as PORT
3. Write the free port to $DIR/DevToolsActivePort (see formatting info on the other bug)
4. exec the real CEF with all the same arguments except with the --remote-debugging-port=0 argument changed to --remote-debugging-port=$PORT

Note that for #4 it is important to exec CEF rather that start a CEF subprocess. This is because ChromeDriver depends on being able to check the state of the browser process, and it the browser process exits then ChromeDriver assumes that it has crashed. It is also helpful so ChromeDriver can kill the browser process if need be.

But it would be better to fix the CEF code itself rather than using the hacky wrapper script.

I spoke in detail with John about this problem. We decided that we would rather not force Chromium derivative apps like CEF and Electron to write the DevToolsActivePort file. Instead, the plan is to allow users to pass in --remote-debugging-port=<PORT> and for us to use that instead. This will require them to start using that flag, but that should not be a very difficult change. Now I will dig into the code for this. 

Regarding this specific problem. I have my test working by doing this hack:
cl/204523402

Thanks for your help Caleb!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/80104bfcec5f4544b8e14538bdb00451995750c8

commit 80104bfcec5f4544b8e14538bdb00451995750c8
Author: Caleb Rouleau <crouleau@chromium.org>
Date: Mon Jul 16 20:35:15 2018

[ChromeDriver] Allow user-defined remote-debugging-port.

Chromium Embedded Framework sometimes uses an in-memory user-data-dir,
so the DevToolsActivePort file is not a viable option for them. We
think it is likely that other Chromium variants, present or future,
may have trouble with the DevToolsActivePort file, so this should
make things easier for them.

Also, fix testConnectToRemoteBrowser to
1. Have retries so it passes in the case of a race condition
for port allocation.
2. Prevent a race with Chrome during teardown.
   -- Note that this race was causing the user-data-dir to
      not be deleted at the end.

Bug:  863247 
Change-Id: I506be26fc2e282b7194afd88afd02efcec65e880
Reviewed-on: https://chromium-review.googlesource.com/1137440
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575408}
[modify] https://crrev.com/80104bfcec5f4544b8e14538bdb00451995750c8/chrome/test/chromedriver/chrome_launcher.cc
[modify] https://crrev.com/80104bfcec5f4544b8e14538bdb00451995750c8/chrome/test/chromedriver/test/run_py_tests.py
[modify] https://crrev.com/80104bfcec5f4544b8e14538bdb00451995750c8/chrome/test/chromedriver/util.py

This should be fixed and released in ChromeDriver 2.41. Not sure when exactly when will release 2.41 though.

Once this is out, the solution is to add argument --remote-debugging-port=<PORT> to chrome options that are passed in when creating the driver. See reference: http://chromedriver.chromium.org/capabilities

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e1900fcf6f18caff57faf059b368e9c2f93edd2c

commit e1900fcf6f18caff57faf059b368e9c2f93edd2c
Author: Caleb Rouleau <crouleau@chromium.org>
Date: Fri Jul 20 17:57:58 2018

[ChromeDriver] Allow user-defined remote-debugging-port.

Chromium Embedded Framework sometimes uses an in-memory user-data-dir,
so the DevToolsActivePort file is not a viable option for them. We
think it is likely that other Chromium variants, present or future,
may have trouble with the DevToolsActivePort file, so this should
make things easier for them.

Also, fix testConnectToRemoteBrowser to
1. Have retries so it passes in the case of a race condition
for port allocation.
2. Prevent a race with Chrome during teardown.
   -- Note that this race was causing the user-data-dir to
      not be deleted at the end.

TBR=crouleau@chromium.org

Bug:  865982 ,  863247 
Change-Id: I506be26fc2e282b7194afd88afd02efcec65e880
Reviewed-on: https://chromium-review.googlesource.com/1137440
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#575408}(cherry picked from commit 80104bfcec5f4544b8e14538bdb00451995750c8)
Reviewed-on: https://chromium-review.googlesource.com/1145560
Cr-Commit-Position: refs/branch-heads/3440@{#729}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
[modify] https://crrev.com/e1900fcf6f18caff57faf059b368e9c2f93edd2c/chrome/test/chromedriver/chrome_launcher.cc
[modify] https://crrev.com/e1900fcf6f18caff57faf059b368e9c2f93edd2c/chrome/test/chromedriver/test/run_py_tests.py
[modify] https://crrev.com/e1900fcf6f18caff57faf059b368e9c2f93edd2c/chrome/test/chromedriver/util.py