It appears the issue is in X11DesktopHandler::ActivateWindow

We set the timestamp to the time the user last clicked or pressed a key in the window:
xclient.xclient.data.l[1] = wm_user_time_ms_;

So, if the user uses the command line to open a new tab in an existing browser, this timestamp becomes out of date and the WM (in my case, Cinnamon) ignores the request.

The other option is to use XRaiseWindow() instead, which I've verified to work in this case.  However, this would steal the focus, even if the user has focus-stealing off in whatever WM they're using.

Another option could be to use 0 for the timestamp, which seems to work on Cinnamon, but would contribute to this bug https://bugs.chromium.org/p/chromium/issues/detail?id=379615.  We shouldn't use the current system time because the timestamp is relative to when the X server started.

IIRC, when you use the command line to interact with an existing browser, it sends an ipc over a pipe. Can you push the current user time from the instance of chrome on the command line to the long lived chrome process?

I agree that would be the right thing to do.  But, the short-lived chrome process doesn't have the time from the X server stored in wm_user_time_ms_ because the user never gets a chance to interact with the browser.  Also, the timestamp given by the X server is relative to when the X process started, so we can't just use gettimeofday() or similar.

Is there any way to ask the X server for the timestamp, or is there a timestamp that might be stored somewhere that I don't know about?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ca3656dc321be956db788c5fc8ee16cd20ed6d86

commit ca3656dc321be956db788c5fc8ee16cd20ed6d86
Author: thomasanderson <thomasanderson@google.com>
Date: Tue May 17 02:02:50 2016

X11: Better timestamp handling for _NET_ACTIVE_WINDOW

Main changes introduced:
1. Get the X server timestamp in the newly created browser process and
send it over IPC to the old process to update wm_user_time_ms

2. Add logic in set_wm_user_time_ms to avoid setting the time to 0 (or
backwards)

3. If wm_user_time_ms == 0 and we try to activate a window, grab the
server time first

BUG= 593516 , 608521 , 379615 

Review-Url: https://codereview.chromium.org/1949393007
Cr-Commit-Position: refs/heads/master@{#394018}

[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/chrome/browser/chrome_browser_main_extra_parts_x11.cc
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/chrome/browser/ui/startup/startup_browser_creator.cc
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/chrome/common/chrome_switches.cc
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/chrome/common/chrome_switches.h
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/tools/metrics/histograms/histograms.xml
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/ui/events/platform/x11/x11_event_source.cc
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/ui/events/platform/x11/x11_event_source.h
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/ui/views/widget/desktop_aura/x11_desktop_handler.cc
[modify] https://crrev.com/ca3656dc321be956db788c5fc8ee16cd20ed6d86/ui/views/widget/desktop_aura/x11_desktop_handler.h