mus: Crash on "...XlibInt.c:245: _XPrivSyncFunction: Assertion `dpy->synchandler == _XPrivSyncFunction' failed"

These seem to be new after syncing to #521367 this morning.
Possibly related to  Issue 791619 , but they seem to be different crashes.
(1) Run "chrome --mus --use-gl=egl" on ToT (a chromeos build on linux-desktop)
(2) Attempt to use the OS/browser for a while (usually < ~1min)
Expected: No crashes
Actual: Crashes randomly, output and callstack below:

msw@msw-linux:/work/chrome-git/src$ out/Default/chrome --mus --use-gl=egl
[104722:104722:1204/101222.367123:ERROR:zygote_host_impl_linux.cc(111)] SUID sandbox binary is missing. Won't be able to adjust OOM scores.
[104722:104744:1204/101223.570593:ERROR:logging_chrome.cc(210)] Unable to create symlink /usr/local/google/home/msw/.config/chromium/test-user/chrome_debug.log pointing at /usr/local/google/home/msw/.config/chromium/test-user/chrome_debug_20171204-101223: File exists (17)
[104722:104722:1204/101223.585103:ERROR:display_manager.cc(1735)] Could not find display:36029742295586560
[104722:104763:1204/101223.678524:ERROR:binder_registry.h(89)] Failed to locate a binder for interface: ui::mojom::VideoDetector
[104722:104722:1204/101223.679391:ERROR:easy_resize_window_targeter.cc(29)] Not implemented reached in gfx::Insets wm::(anonymous namespace)::InsetsWithOnlyNegativeValues(const gfx::Insets &)
[104722:104722:1204/101223.785038:ERROR:input_method_manager_impl.cc(1031)] IMEEngine for "fgoepimhcoialccpbmpnnblemnepkkao" is not registered
libEGL warning: DRI2: failed to authenticate
[104758:104758:1204/101224.186069:ERROR:sandbox_linux.cc(375)] InitializeSandbox() called with multiple threads in process gpu-process.
[104758:104758:1204/101224.557091:ERROR:gl_context_egl.cc(307)] eglSwapInterval failed with error EGL_SUCCESS
[104722:104722:1204/101227.528750:ERROR:tab_manager_delegate_chromeos.cc(82)] Set OOM score error: 
[104722:104722:1204/101229.826268:ERROR:tab_manager_delegate_chromeos.cc(82)] Set OOM score error: 
[104722:104722:1204/101233.809608:ERROR:tab_manager_delegate_chromeos.cc(82)] Set OOM score error: 
[104722:104722:1204/101233.809660:ERROR:tab_manager_delegate_chromeos.cc(82)] Set OOM score error: 
-git/src/out/Default/chrome --mus --use-gl=egl: ../../src/XlibInt.c:245: _XPrivSyncFunction: Assertion `dpy->synchandler == _XPrivSyncFunction' failed.
Received signal 6
#0 0x7efeb73b385c base::debug::StackTrace::StackTrace()
#1 0x7efeb73b3351 base::debug::(anonymous namespace)::StackDumpSignalHandler()
#2 0x7efeb753a330 <unknown>
#3 0x7efeaacdec37 gsignal
#4 0x7efeaace2028 abort
#5 0x7efeaacd7bf6 <unknown>
#6 0x7efeaacd7ca2 __assert_fail
#7 0x7efeaa4c3ed0 <unknown>
#8 0x7efeaa4a14de XDefineCursor
#9 0x7efeb48aee5d _ZN4base8internal7InvokerINS0_9BindStateIMN7content27IndexedDBActiveBlobRegistryEFvllEJNS_7WeakPtrIS4_EEllEEEFvvEE7RunImplIRKS6_RKNSt3__15tupleIJS8_llEEEJLm0ELm1ELm2EEEEvOT_OT0_NSF_16integer_sequenceImJXspT1_EEEE
#10 0x7efeb73b4135 base::debug::TaskAnnotator::RunTask()
#11 0x7efeb73e4749 base::internal::IncomingTaskQueue::RunTask()
#12 0x7efeb73e824b base::MessageLoop::RunTask()
#13 0x7efeb73e85e3 base::MessageLoop::DeferOrRunPendingTask()
#14 0x7efeb73e8876 base::MessageLoop::DoWork()
#15 0x7efeb73eada9 base::MessagePumpLibevent::Run()
#16 0x7efeb73e7b49 base::MessageLoop::Run()
#17 0x7efeb741c319 base::RunLoop::Run()
#18 0x7efeb745c707 base::Thread::Run()
#19 0x7efeb745ccbc base::Thread::ThreadMain()
#20 0x7efeb7453a5f base::(anonymous namespace)::ThreadFunc()
#21 0x7efeb7532184 start_thread
#22 0x7efeaada5ffd clone
  r8: fefefefefefefeff  r9: fefefefefefefeff r10: 0000000000000008 r11: 0000000000000206
 r12: 00007efeaa5309b8 r13: 00007efeaa530a70 r14: 0000307b70b0c3a0 r15: 00007efeb56568f0
  di: 0000000000019912  si: 000000000001993b  bp: 00007efeaae2c018  bx: 00007efe8f713000
  dx: 0000000000000006  ax: 0000000000000000  cx: 00007efeaacdec37  sp: 00007efe8d561b98
  ip: 00007efeaacdec37 efl: 0000000000000206 cgf: 0000000000000033 erf: 0000000000000000
 trp: 0000000000000000 msk: 0000000000000000 cr2: 0000000000000000
[end of stack trace]
Calling _exit(1). Core file will not be generated.

I wonder if this is fallout related to running mus without viz?
https://chromium-review.googlesource.com/c/chromium/src/+/798776