Add comment and prevent redundant event-state set for VSyncDPC
Add comment and prevent redundant event-state set for VSyncDPC

Signed-off-by: Zuoming Shi <8a7f94c83ebfb575049217889adb521a88ae59cb@gmail.com>

GameTechDev/PresentMon,GameTechDev/PresentMon,GameTechDev/PresentMon,GameTechDev/PresentMon