Fixed segmentation fault. Because currently return null when call views::LinuxUI::instance().

ui/views/widget/desktop_aura/desktop_screen_x11.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11.cc b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
index e37e602ad3d252d63d95b5ebe13271bf5aa7392f..fc477e61d5d2d745dc4a8416cfe361196d4c04fc 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
@@ -287,8 +287,7 @@ std::vector<gfx::Display> DesktopScreenX11::BuildDisplaysFromXRandRInfo() {
 
   // As per-display scale factor is not supported right now,
   // the X11 root window's scale factor is always used.
-  const float device_scale_factor =
-      views::LinuxUI::instance()->GetDeviceScaleFactor();
+  const float device_scale_factor = GetDeviceScaleFactor();
   for (int i = 0; i < resources->noutput; ++i) {
     RROutput output_id = resources->outputs[i];
     gfx::XScopedPtr<XRROutputInfo,