Able to reproduce.  I'll revert the CL and reland with a fix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/13a1bab95fc7bc49a2ee8aa160ce83fa3aac38ca

commit 13a1bab95fc7bc49a2ee8aa160ce83fa3aac38ca
Author: Thomas Anderson <thomasanderson@chromium.org>
Date: Fri Dec 22 20:46:14 2017

Revert "Remove ui::X11EventSource::BlockUntilWindowMapped"

This reverts commit f93b585a4faa911f85dfd86c62d1523308b5bdba.

Reason for revert: Windows don't get shown

Original change's description:
> Remove ui::X11EventSource::BlockUntilWindowMapped
> 
> This CL removes BlockUntilWindowMapped() and the 2 references to it.
> 
> The first reference, in X11WholeScreenMoveLoop, waits until an offscreen window
> is mapped.  The window is override-redirect (so there's not WM that
> asynchronously decides when to map the window), so any operations done on the
> window should succeed after the window is mapped since the X server processes
> events in sequence.
> 
> The second reference is from X11WindowBase.  A similar removal was done in
> DesktopWindowTreeHostX11 in [1], so BlockUntilWindowMapped() shouldn't be needed
> here either.
> 
> [1] https://chromium.googlesource.com/chromium/src/+/662c24fc6debb33ee34a927d21dc26154b8973d6
> 
> R=​sadrul@chromium.org
> 
> Change-Id: I251e67839dd5216f5164a103a82ad8a906811a03
> Bug: None
> Reviewed-on: https://chromium-review.googlesource.com/823212
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#525869}

TBR=sadrul@chromium.org,thomasanderson@chromium.org

Change-Id: I7bc83f409171941ce812ab09e0191b935127a38b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  797358 
Reviewed-on: https://chromium-review.googlesource.com/842685
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526056}
[modify] https://crrev.com/13a1bab95fc7bc49a2ee8aa160ce83fa3aac38ca/ui/events/platform/x11/x11_event_source.cc
[modify] https://crrev.com/13a1bab95fc7bc49a2ee8aa160ce83fa3aac38ca/ui/events/platform/x11/x11_event_source.h
[modify] https://crrev.com/13a1bab95fc7bc49a2ee8aa160ce83fa3aac38ca/ui/platform_window/x11/x11_window_base.cc
[modify] https://crrev.com/13a1bab95fc7bc49a2ee8aa160ce83fa3aac38ca/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc

 Issue 797565  has been merged into this issue.

Fixed.  going to reland with the change now

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/663caaea27c87452609753308ff00b5798703b60

commit 663caaea27c87452609753308ff00b5798703b60
Author: Tom Anderson <thomasanderson@chromium.org>
Date: Wed Jan 03 01:37:50 2018

Reland "Remove ui::X11EventSource::BlockUntilWindowMapped"

This reverts commit 13a1bab95fc7bc49a2ee8aa160ce83fa3aac38ca.

Reason for revert:  Windows are shown after XFlush().

> This reverts commit f93b585a4faa911f85dfd86c62d1523308b5bdba.
>
> Reason for revert: Windows don't get shown
>
> Original change's description:
> > Remove ui::X11EventSource::BlockUntilWindowMapped
> >
> > This CL removes BlockUntilWindowMapped() and the 2 references to it.
> >
> > The first reference, in X11WholeScreenMoveLoop, waits until an offscreen window
> > is mapped.  The window is override-redirect (so there's not WM that
> > asynchronously decides when to map the window), so any operations done on the
> > window should succeed after the window is mapped since the X server processes
> > events in sequence.
> >
> > The second reference is from X11WindowBase.  A similar removal was done in
> > DesktopWindowTreeHostX11 in [1], so BlockUntilWindowMapped() shouldn't be needed
> > here either.
> >
> > [1] https://chromium.googlesource.com/chromium/src/+/662c24fc6debb33ee34a927d21dc26154b8973d6
> >
> > R=​sadrul@chromium.org
> >
> > Change-Id: I251e67839dd5216f5164a103a82ad8a906811a03
> > Bug: None
> > Reviewed-on: https://chromium-review.googlesource.com/823212
> > Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> > Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#525869}
>
> TBR=sadrul@chromium.org,thomasanderson@chromium.org
>
> Change-Id: I7bc83f409171941ce812ab09e0191b935127a38b
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug:  797358 
> Reviewed-on: https://chromium-review.googlesource.com/842685
> Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#526056}

R=sadrul@chromium.org
BUG= 797358 

Change-Id: I601defea876f5547b045e8584cb592366c36f4ac
Reviewed-on: https://chromium-review.googlesource.com/842474
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526571}
[modify] https://crrev.com/663caaea27c87452609753308ff00b5798703b60/ui/events/platform/x11/x11_event_source.cc
[modify] https://crrev.com/663caaea27c87452609753308ff00b5798703b60/ui/events/platform/x11/x11_event_source.h
[modify] https://crrev.com/663caaea27c87452609753308ff00b5798703b60/ui/platform_window/x11/x11_window_base.cc
[modify] https://crrev.com/663caaea27c87452609753308ff00b5798703b60/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc