Comment 9 for bug 1381625

Issue can be reproduced with below builds, please refer the results below:

[Tested images for verification]
Stock 14.04.1 [ubuntu-14.04.1-desktop-amd64.iso] -> Failed
Stock 14.10 [ubuntu-14.10-desktop-amd64.iso] -> Failed
15.04 daily build @1/13 [vivid-desktop-amd64.iso] -> Failed

[Test Case / Reproduce Steps]
1. Install Image
2. Press System's brightness hotkey to adjust the brightness level to the lowest or
3. Go to System "Settings" -> "Brightness & Lock" to adjust brightness level to the lowest
4. Check if the screen display still has backlight

[Other Info]
1. For 14.04, due to bug#1332379, (https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1332379), the brightness cannot be adjusted after the system freshly installed. After adding kernel parameter "video.use_native_backlight=1" it then can work.
2. Test unit: Dell Haswell ULT system