crash when dragging window to another display. I haven't tested on device yet, and this could be specific to x11/desktop.

besecting now. adding a few folks who may have some idea.

#0  aura::Window::IsRootWindow (this=0x0) at ../../ui/aura/window.h:131
#1  0x00007ffff7f26249 in aura::Window::GetRootWindow (this=0x0) at ../../ui/aura/window.cc:216
#2  0x00007ffff7f28a3a in aura::Window::ConvertPointToTarget (source=0x1d8e6c7596a0, target=0x0, point=0x7fffffff9250)
    at ../../ui/aura/window.cc:443
#3  0x00007ffff7a64e4d in ash::(anonymous namespace)::ConvertPointToParent (window=0x1d8e6c7596a0, point=...)
    at ../../ash/wm/toplevel_window_event_handler.cc:74
#4  0x00007ffff7a6410b in ash::ToplevelWindowEventHandler::HandleDrag (this=0x1d8e6c7e5c50, target=0x1d8e6c7596a0, event=
    0x7fffffffb230) at ../../ash/wm/toplevel_window_event_handler.cc:542
#5  0x00007ffff7a63d9d in ash::ToplevelWindowEventHandler::OnMouseEvent (this=0x1d8e6c7e5c50, event=0x7fffffffb230)
    at ../../ash/wm/toplevel_window_event_handler.cc:210
#6  0x00007ffff090f0f7 in ui::EventHandler::OnEvent (this=0x1d8e6c7e5c50, event=0x7fffffffb230)
    at ../../ui/events/event_handler.cc:29
#7  0x00007ffff090ab70 in ui::EventDispatcher::DispatchEvent (this=0x7fffffff9888, handler=0x1d8e6c7e5c50, event=0x7fffffffb230)
    at ../../ui/events/event_dispatcher.cc:191
#8  0x00007ffff090a925 in ui::EventDispatcher::DispatchEventToEventHandlers (this=0x7fffffff9888, list=0x7fffffff98a0, 
    event=0x7fffffffb230) at ../../ui/events/event_dispatcher.cc:170
#9  0x00007ffff090a434 in ui::EventDispatcher::ProcessEvent (this=0x7fffffff9888, target=0x1d8e6c7596c8, event=0x7fffffffb230)
    at ../../ui/events/event_dispatcher.cc:127
#10 0x00007ffff090a262 in ui::EventDispatcherDelegate::DispatchEventToTarget (this=0x1d8e6c771160, target=0x1d8e6c7596c8, 
    event=0x7fffffffb230) at ../../ui/events/event_dispatcher.cc:86
#11 0x00007ffff090a142 in ui::EventDispatcherDelegate::DispatchEvent (this=0x1d8e6c771160, target=0x1d8e6c7596c8, 
    event=0x7fffffffb230) at ../../ui/events/event_dispatcher.cc:58
#12 0x00007ffff090fdab in ui::EventProcessor::OnEventFromSource (this=0x1d8e6c771160, event=0x7fffffffb230)
    at ../../ui/events/event_processor.cc:35
#13 0x00007ffff0910e15 in ui::EventSource::DeliverEventToProcessor (this=0x1d8e6c1c0438, event=0x7fffffffb230)
    at ../../ui/events/event_source.cc:73
#14 0x00007ffff0910a9c in ui::EventSource::SendEventToProcessor (this=0x1d8e6c1c0438, event=0x7fffffffb230)
    at ../../ui/events/event_source.cc:51
#15 0x00007ffff78541fb in ash::AshWindowTreeHostX11::TranslateAndDispatchLocatedEvent (this=0x1d8e6c1c0420, event=0x7fffffffb230)
    at ../../ash/host/ash_window_tree_host_x11.cc:235
#16 0x00007ffff7f5007a in aura::WindowTreeHostX11::DispatchXI2Event (this=0x1d8e6c1c0430, event=@0x7fffffffc880: 0x7fffffffc9f8)
    at ../../ui/aura/window_tree_host_x11.cc:511
#17 0x00007ffff7f4fb51 in aura::WindowTreeHostX11::DispatchEvent (this=0x1d8e6c1c0430, event=@0x7fffffffc940: 0x7fffffffc9f8)
    at ../../ui/aura/window_tree_host_x11.cc:316
#18 0x00007ffff086eb8f in ui::PlatformEventSource::DispatchEvent (this=0x1d8e6c1bf928, platform_event=0x7fffffffc9f8)
    at ../../ui/events/platform/platform_event_source.cc:83
#19 0x00007fffea2ff894 in ui::X11EventSourceGlib::ProcessXEvent (this=0x1d8e6c1bf920, xevent=0x7fffffffc9f8)
    at ../../ui/events/platform/x11/x11_event_source_glib.cc:65
---Type <return> to continue, or q <return> to quit---
#20 0x00007fffea2f2aca in ui::X11EventSource::ExtractCookieDataDispatchEvent (this=0x1d8e6c1bf9d0, xevent=0x7fffffffc9f8)
    at ../../ui/events/platform/x11/x11_event_source.cc:148
#21 0x00007fffea2f2a01 in ui::X11EventSource::DispatchXEvents (this=0x1d8e6c1bf9d0)
    at ../../ui/events/platform/x11/x11_event_source.cc:115
#22 0x00007fffea2ffa55 in ui::(anonymous namespace)::XSourceDispatch (source=0x1d8e6c1fd180, unused_func=0x0, data=0x1d8e6c1bf9d0)
    at ../../ui/events/platform/x11/x11_event_source_glib.cc:41
#23 0x00007fffe617ece5 in g_main_dispatch (context=0x1d8e6c119a70) at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:3064
#24 g_main_context_dispatch (context=context@entry=0x1d8e6c119a70) at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:3663
#25 0x00007fffe617f048 in g_main_context_iterate (context=context@entry=0x1d8e6c119a70, block=block@entry=1, 
    dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:3734
#26 0x00007fffe617f0ec in g_main_context_iteration (context=0x1d8e6c119a70, may_block=1)
    at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:3795