Override for the CPU performance tier

Setting this policy allows enterprises to override the value returned by the CPU Performance API (i.e., navigator.cpuPerformance, please see https://github.com/WICG/cpu-performance for details). If this policy is set, the value of navigator.cpuPerformance will be overridden to the specified value. If the policy is not set, then the default performance tier calculation is used. The possible values for this policy are 0 to 4.