Potter Stewart on sexting?

Potter Stewart famously said:
"I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description ["hard-core pornography"]; and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that."
—Justice Potter Stewart, concurring opinion in Jacobellis v. Ohio 378 U.S. 184 (1964), regarding possible obscenity in The Lovers.
http://en.wikipedia.org/wiki/I_know_it_when_I_see_it

Imagine that 30 years ago, before smart phones, a teenage girl took a picture of herself in front of a mirror with an old fashioned box camera – every three months – to keep track of how she was growing.  Imagine she showed other girls – or they trade pictorial notes.  Imagine she passed a picture on to a boy she could legally have sex with.

Would Potter Stewart have taken this for child pornography?