Auto-brightness only applied a half-second after wakeup

Steps:
* enable auto brightness
* go to a bright room
* suspend the phone
* go to a dark room
* resume the phone

Expected:
* phone wakes with a brightness level appropriate for the dark room

Current:
* phone wakes with the old brightness level
* and changes to the new level half a second later

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: unity-system-compositor 0.0.5+15.04.20141204-0ubuntu1
Uname: Linux 3.4.67 armv7l
ApportVersion: 2.15-0ubuntu3
Architecture: armhf
Date: Tue Jan 6 11:23:24 2015
GraphicsCard:

InstallationDate: Installed on 2014-12-17 (20 days ago)
InstallationMedia: Ubuntu Vivid Vervet (development branch) - armhf (20141217-020204)
SourcePackage: unity-system-compositor
UpgradeStatus: No upgrade log present (probably fresh install)
version.libdrm: libdrm2 2.4.58-2
version.lightdm: lightdm 1.13.0-0ubuntu2
version.mesa: libegl1-mesa-dev N/A