Created attachment 8828530 [details]
User Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0
Build ID: 20170118123726
Steps to reproduce:
step 1: Launch Firefox
step 2: Open about:config and set the value of layers.acceleration.disabled to true, then restart the browser.
step 3: Verify that the pref change has been applied, following browser restart.
The value of the AzureContentBackend field is cairo in about:support.
The value of the AzureContentBackend field is skia in about:support.
I cannot reproduce this with the newest version of Nightly with the following specs:
Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:54.0) Gecko/20100101 Firefox/54.0
Can you try installing the newest version of Nightly and see if you can reproduce the issue?