Firefox ALWAYS uses separate graphics chip & overheating 2011MBP motherboard
I DO NOT have "use hardware acceleration when available" turned on.
But OSX Activity Moniter says that Firefox "requires high performance GPU" -- which means that Firefox is going to ruin my motherboard by overheating the AMD Radeon GPU in my 2011 Macbook Pro. Search for "Radeongate" for details of this Apple design failure.
I have an app that will toggle use of the GPU except that some apps, Firefox being one, do not allow it to be turned off. Has to do with some kind of script call, which could be programmed another way.