UserAgent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0

Steps to reproduce the problem:
1. Xvfb :2 -screen 0 1920x1080x24 &
2. DISPLAY=:2 ./browser_tests --gtest_filter=ExtensionWindowLastFocusedTest.NoTabIdForDevToolsAndAppWindows

What is the expected behavior?
Test should pass as it passes when executed without Xvfb

What went wrong?
Test fails with error messages:

../../chrome/browser/extensions/api/tabs/tabs_test.cc:983: Failure
Expected equality of these values:
  popup_browser_window_id
    Which is: 5
  api_test_utils::GetInteger(result.get(), "id")
    Which is: 3

../../chrome/browser/extensions/api/tabs/tabs_test.cc:985: Failure
Expected equality of these values:
  "popup"
  api_test_utils::GetString(result.get(), "type")
    Which is: "normal"

Did this work before? N/A 

Chrome version: r603403  Channel: n/a
OS Version: Debian Jessie
Flash Version: Shockwave Flash 31.0 r0

This test is failing when executed in headless mode using Xvfb. Complete log of the execution can be seen at:
http://www.rt-rk.com/mips-buildbot/builders/build_and_test_chromium_browser_tests_for_MIPS/builds/10/steps/Run%20browser_tests_26/logs/stdio

This is execution on MIPS Creator CI20 platform, but same issue was reproduced in X86-64 Ubuntu 16.04 system.

Used versions of xvfb:

1.18.4-0ubuntu0.8 on X86-64 Ubuntu
1.16.4-1+deb8u2 on MIPS Debian Jessie

This issue was already reported on chromium-dev:
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/AaKy_NGEslg