Comment 10 for bug 1238695

Taking a look at this, I see it on my tegra3.

I've eliminated:
#1 Application switching (this seems okay with mir_demo_server_shell)

#2 logcat messages about:
E/hwcomposer( 6696): Failed to set DIDIM level
E/hwcomposer( 6696): /sys/class/graphics/fb0/device/smartdimmer/enable: open failed, errno = 13
these don't really seem to affect anything

#3 Display loop hangs
During the flicker/static image, the display loop is still updating in response to touch events.

The most likely cause is something is going awry with screenshotting on this device. The problem happens around the time unity8 would take a screenshot, and I see messages like:
file:///usr/lib/arm-linux-gnueabihf/qt5/imports/Unity-Mir/Unity/Application/ApplicationImage.qml:37:5: QML QQuickImage: Failed to get image from provider: image://screenshot/ubuntu-system-settings