See  issue 833148  for a repro, but in general, the problem is that new tabs always seem to cause activation, via chrome::Navigate

https://cs.chromium.org/chromium/src/chrome/browser/ui/browser_navigator.cc?rcl=f79f0834a69bb705e91fda8fc2e5f7668f4dd6d0&l=472


If  issue 833148  is fixed, just repro with --disable-popup-blocking or use settings.