Comment 5 for bug 1521403

Some more data points...

I disabled the screen blanking, but that made no difference.

But with the screen not blanked, I started an X app through Xmir and left U8 idle and observed at almost exactly 10 minutes of idle time, U8 crashed. This is what was in unity8.log at the time of the crash:

[2017-01-10 15:09:10.552229] mirserver: New display configuration:
[2017-01-10 15:09:10.552346] mirserver: Output 36: LVDS connected, used
[2017-01-10 15:09:10.552434] mirserver: Physical size 13,0" 290x160mm
[2017-01-10 15:09:10.552493] mirserver: Current mode 1366x768 60,00Hz
[2017-01-10 15:09:10.552549] mirserver: Preferred mode 1366x768 60,00Hz
[2017-01-10 15:09:10.552594] mirserver: Logical position +0+0
[2017-01-10 15:09:10.552676] mirserver: Output 43: VGA disconnected
[2017-01-10 15:09:10.552739] mirserver: Output 46: HDMI-A disconnected
[2017-01-10 15:09:10.552799] mirserver: Output 51: DisplayPort disconnected
[2017-01-10:15:09:10.553] qtmir.screens: QtCompositor::stop
[2017-01-10:15:09:10.554] qtmir.screens: ScreensModel::onCompositorStopping
[2017-01-10:15:09:10.554] qtmir.screens: ScreenWindow::setExposed 0x1c1e510 false 0x7f4ed824f020
[2017-01-10:15:09:10.581] qtmir.screens: ScreensModel::update
[2017-01-10:15:09:10.582] qtmir.screens: Screen::setMirDisplayBuffer Screen(0x7f4ed824f010) 0x7f4ed815cb40 0x7f4ed815cc90
[2017-01-10:15:09:10.582] qtmir.screens: =======================================
[2017-01-10:15:09:10.582] qtmir.screens: Screen(0x7f4ed824f010) - id: 36 geometry: QRect(0,0 1366x768) window: 0x1c1e510 type: "LVDS" scale: 1
[2017-01-10:15:09:10.582] qtmir.screens: =======================================
[2017-01-10:15:09:10.587] qtmir.screens: QtCompositor::start
[2017-01-10:15:09:10.587] qtmir.screens: ScreensModel::onCompositorStarting
[2017-01-10:15:09:10.587] qtmir.screens: ScreensModel::update
[2017-01-10:15:09:10.587] qtmir.screens: =======================================
[2017-01-10:15:09:10.587] qtmir.screens: Screen(0x7f4ed824f010) - id: 36 geometry: QRect(0,0 1366x768) window: 0x1c1e510 type: "LVDS" scale: 1
[2017-01-10:15:09:10.587] qtmir.screens: =======================================
[2017-01-10:15:09:10.587] qtmir.screens: ScreenWindow::setExposed 0x1c1e510 true 0x7f4ed824f020
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::system_error> >'
  what(): Nested Mir Display Error: Failed to update EGL surface: EGL_BAD_CONTEXT (0x3006)