"controlled a Dragon as you cast" ​ vs ​ sacrificing while casting

[Phasmoid]

The active player controls exactly 1 Dragon, and that Dragon is a creature.
That player casts a Dragon-check spell
https://scryfall.com/search?q=oracle%3Acontrolled+oracle%3A%22as+you+cast%22
, ​ and as part of that casting process, sacrifices
that player's Dragon to pay a mana ability's cost
https://scryfall.com/search?q=oracle%3A%22sacrifice+a+creature%3A+Add%22
and does not reveal a Dragon card from that player's hand.

Can that player time things so as to get the
"If you revealed a Dragon card or controlled a Dragon as you cast"
part?

[Fox]

The first part of casting a spell is announcing it, it's targets, and modes. You passed the dragon check here, at the point of figuring out what the spell was.

Next step: pay the costs.