Lanai : Performance of LargeText renderperf tests dipped

Performace of the LargeTextNoAA, LargeTextLCD, LargeTextGray dipped from build of 31st Oct and 17th Nov.

performance results for metal after the build of 31st Oct
LargeTextNoAA : 5.04 FPS
LargeTextLCD : 5.00 FPS
LargeTextGray : 5.02 FPS

performance results for metal after the build of 17th Nov
LargeTextNoAA : 1.93 FPS
LargeTextLCD : 1.94 FPS
LargeTextGray : 1.93 FPS

performance results for opengl
LargeTextNoAA : 0.21 FPS
LargeTextLCD : 0.21 FPS
LargeTextGray : 0.21 FPS

Tested on MacMini 10.14 with uiScale=2 on default non-retina display.