RGBX windows become discoloured (more white or translucent) and corrupt in the Unity8 window switcher

Also, in a stroke of fragment shader weirdness, the offending windows appear clear through the Alt+Tab switcher's otherwise blurred background.

In case it's not yet obvious - the issue with RGBX windows is the X byte is uninitialized so needs to be ignored, rather than interpreting it as A for alpha.

How do I reproduce this Daniel?

Any window with a non-1.0 (less than 0xff) alpha or X channel gets discoloured when alt+tabbing:
  mir_demo_client_egltriangle -b 0.2 -- --desktop_file_hint=unity8

And you have to keep in mind that the 'X' byte might be uninitialized, so another good test case is:
  Xmir :0 -rootless -flatten -sw --desktop_file_hint=unity8
  env DISPLAY=:0 gedit
and then Alt+Tab.

Observed: Parts of the window in the switcher are discoloured/whiter. This is Unity8 treating the uninitialized X byte as an alpha byte. Although even RGBA windows get discoloured with low values of A.
Observed: In the background the fullscreen blur is also faulty -- it's clearer and not blurred in the same regions as are affected by the first issue.

Status changed to 'Confirmed' because the bug affects multiple users.