Open terminal and type:
$ sudo gedit /etc/init.d/ondemand
When gedit opens, paste the following block of information at the very bottom:
for CPU_THRESHOLD in /sys/devices/system/cpu/cpu*/cpufreq/ondemand/up_threshold
[ -f $CPU_THRESHOLD ] || continue
echo -n 30 > $CPU_THRESHOLD
See the image below for the exact placement of the code, notice that it is placed below the "esac" that is already present.
If you're having problems exiting flash, you can try changing the niceness value to something lower. The original value is echo -n 40, I was able to keep HQ video playback and better system stability at echo -n 30 so changed that to the default value above.
After you're done editing that file, save it and we'll finish up the rest of the steps in terminal:
$ sudo mkdir /etc/adobe
$ echo “OverrideGPUValidation=true” > ~/mms.cfg
$ sudo mv ~/mms.cfg /etc/adobe/
Now reboot and you *should* be able to watch full screen videos now lag and stutter free. Enjoy!