Comment 1 for bug 1675331

Bisected. It change came from:

------------------------------------------------------------
revno: 4103 [merge]
author: Christopher James Halse Rogers <email address hidden>
committer: Tarmac
branch nick: development-branch
timestamp: Wed 2017-03-22 07:01:56 +0000
message:
  Clarify KMS display configuration responsibilities.

  This moves responsibility for converting between KMS hardware state and Mir DisplayOutputConfiguration to KMSOutput, moves DisplayConfigurationOutputId → KMSOutput lookup into KMSDisplayConfiguration, and makes KMSOutputContainer responsible for maintaining the set of KMSOutput as they appear and disappear.

  Approved by mir-ci-bot, Kevin DuBois, Alan Griffiths.
------------------------------------------------------------