110303 WARNING: XPCOM objects created/destroyed from static ctor/dtor: file xpcom/base/nsTraceRefcnt.cpp, line 198

This warning [1] shows up in the following test suites:

  7970 - test-macosx1014-64/debug-web-platform-tests-e10s-2 wpt2
  7404 - test-macosx1014-64/debug-web-platform-tests-e10s-13 wpt13
  7279 - test-macosx1014-64/debug-web-platform-tests-e10s-16 wpt16
  6920 - test-macosx1014-64/debug-web-platform-tests-e10s-7 wpt7
  5992 - test-macosx1014-64/debug-web-platform-tests-e10s-10 wpt10
  5287 - test-macosx1014-64/debug-web-platform-tests-e10s-15 wpt15
  5204 - test-macosx1014-64/debug-web-platform-tests-e10s-11 wpt11
  5108 - test-macosx1014-64/debug-web-platform-tests-e10s-6 wpt6
  4840 - test-macosx1014-64/debug-web-platform-tests-e10s-4 wpt4
  4664 - test-macosx1014-64/debug-web-platform-tests-e10s-1 wpt1
  4432 - test-macosx1014-64/debug-web-platform-tests-e10s-8 wpt8
  4416 - test-macosx1014-64/debug-web-platform-tests-e10s-5 wpt5
  4388 - test-macosx1014-64/debug-web-platform-tests-e10s-9 wpt9
  4328 - test-macosx1014-64/debug-web-platform-tests-e10s-3 wpt3
  3956 - test-macosx1014-64/debug-web-platform-tests-e10s-14 wpt14
  2811 - test-macosx1014-64/debug-web-platform-tests-e10s-12 wpt12
  1472 - test-macosx1014-64/debug-reftest-e10s-4 R4
  1468 - test-macosx1014-64/debug-reftest-e10s-3 R3
  1436 - test-macosx1014-64/debug-reftest-e10s-2 R2
  1426 - test-macosx1014-64/debug-web-platform-tests-wdspec-e10s-1 Wd1
  1368 - test-macosx1014-64/debug-reftest-e10s-1 R1
   996 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-4 bc4
   916 - test-macosx1014-64/debug-web-platform-tests-reftests-e10s-1 Wr1
   888 - test-macosx1014-64/debug-web-platform-tests-wdspec-e10s-2 Wd2
   828 - test-macosx1014-64/debug-web-platform-tests-reftests-e10s-6 Wr6
   820 - test-macosx1014-64/debug-web-platform-tests-reftests-e10s-5 Wr5
   780 - test-macosx1014-64/debug-web-platform-tests-reftests-e10s-2 Wr2
   740 - test-macosx1014-64/debug-web-platform-tests-reftests-e10s-4 Wr4
   720 - test-macosx1014-64/debug-web-platform-tests-reftests-e10s-3 Wr3
   676 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-3 bc3
   672 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-2 bc2
   668 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-8 bc8
   652 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-7 bc7
   648 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-9 bc9
   636 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-10 bc10
   620 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-5 bc5
   600 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-6 bc6
   596 - test-macosx1014-64/debug-marionette-e10s Mn
   588 - test-macosx1014-64/debug-mochitest-e10s-5 5
   472 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-1 bc1
   436 - test-macosx1014-64/debug-mochitest-e10s-2 2
   432 - test-macosx1014-64/debug-mochitest-e10s-3 3
   368 - test-macosx1014-64/debug-mochitest-e10s-1 1
   368 - test-macosx1014-64/debug-mochitest-e10s-4 4
   272 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-3 dt3
   236 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-6 dt6
   234 - test-macosx1014-64/debug-firefox-ui-functional-local-e10s en-US
   228 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-5 dt5
   228 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-2 dt2
   200 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-1 dt1
   160 - test-macosx1014-64/debug-mochitest-chrome-1proc-1 c1
   156 - test-macosx1014-64/debug-mochitest-media-spi-e10s-1 mda1
   152 - test-macosx1014-64/debug-mochitest-media-spi-e10s-2 mda2
   136 - test-macosx1014-64/debug-mochitest-media-e10s-1 mda1
   132 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-4 dt4
   120 - test-macosx1014-64/debug-mochitest-media-e10s-2 mda2
   108 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-7 dt7
   104 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-11 bc11
    86 - test-macosx1014-64/debug-telemetry-tests-client-e10s c
    76 - test-macosx1014-64/debug-mochitest-chrome-1proc-2 c2
    68 - test-macosx1014-64/debug-gtest-1proc GTest
    60 - test-macosx1014-64/debug-mochitest-gpu-e10s gpu
    60 - test-macosx1014-64/debug-mochitest-webgl1-core-e10s gl1c
    44 - test-macosx1014-64/debug-mochitest-browser-chrome-e10s-12 bc12
    36 - test-macosx1014-64/debug-mochitest-remote-e10s remote
    36 - test-macosx1014-64/debug-mochitest-devtools-chrome-e10s-8 dt8
    28 - test-macosx1014-64/debug-crashtest-e10s C
    14 - test-macosx1014-64/debug-firefox-ui-functional-remote-e10s en-US
    12 - test-macosx1014-64/debug-mochitest-webgl1-ext-e10s gl1e
    12 - test-macosx1014-64/debug-mochitest-webgl2-core-e10s gl2c
     8 - test-macosx1014-64/debug-mochitest-a11y-1proc a11y
     8 - test-macosx1014-64/debug-marionette-media-e10s MnM

It shows up in 20310 tests. A few of the most prevalent:

  4664 - [e10s] Shutdown
   162 - [e10s] /webdriver/tests/new_session/create_alwaysMatch.py
   162 - [e10s] /webdriver/tests/new_session/create_firstMatch.py
    84 - [e10s] browser/base/content/test/tabs/browser_privilegedmozilla_process_pref.js
    60 - [e10s] gfx/layers/apz/test/mochitest/browser_test_group_fission.js
    60 -        browser/components/shell/test/test_headless_screenshot.html
    52 - [e10s] /scroll-to-text-fragment/scroll-to-text-fragment.html
    48 - [e10s] /webdriver/tests/new_window/user_prompts.py
    44 - [e10s] browser/base/content/test/tabs/browser_new_tab_in_privilegedabout_process_pref.js
    42 - [e10s] js/xpconnect/tests/marionette/test_loader_global_sharing.py TestLoaderGlobalSharing.test_global_sharing_settings

[1] https://hg.mozilla.org/mozilla-central/annotate/a3a081ae714f1123bdc23c9d9ef53dfaa783a8de/xpcom/base/nsTraceRefcnt.cpp#l198