Red-Eyes Darkness Metal Dragon
"You can remove from play 1 Dragon-Type monster you control to Special Summon this card. Once per turn, during your Main Phase, you can Special Summon 1 Dragon-Type monster, except "Red-Eyes Darkness Metal Dragon", from your hand or Graveyard."
Book Of Moon
"Flip 1 face-up monster on the field into face-down Defense Position."
Player 1 - Activates the effect of REDMD to Special Summon Masked Dragon from the grave.
Player 2 - Chains Book Of Moon to the effect of REDMD.
Now, REDMD would first be flipped face-down in the Chain, and then the effect of REDMD would go to resolve. My question here is, is REDMD required to be face-up at the time of his effects resolution, or will the monster still be Special Summoned even though REDMD is now face-down? I figure since REDMD doesn't specify a need to be face-up at time of resolution, Masked Dragon would still be revived, but confirmation would be appreciated.