The acoustic version of Gotta Be You on A Year In The Making. Near the end, they 
sing this with Niall playing guitar. This is it:

No capo

Intro: 
G (320003@1)Cadd9 (x32030@1)G (320003@1)D (xx0232@1)GGirl (320003@1)I see it in your eyes you're disappointed
Cadd9
Cause I'm the foolish one that you anointed
G (320003@1)                DWith (xx0232@1)your heart, I tore it apart
                GAnd (320003@1)girl what a mess I made upon your innocence
Cadd9
And no woman in the world deserves this
    G (320003@1)                      DBut (xx0232@1)here I am asking you for one more chance

G (320003@1)           Cadd9I'll (x32030@1)be here by your side
          G (320003@1)           DNo (xx0232@1)more fears no more crying
           G (320003@1)          Cadd9But (x32030@1)if you walk away I know I'll fade
               G (320003@1)        DCause (xx0232@1)there is nobody else

G  Cadd9  G  Cadd9
It's gotta be you, only you
              G (320003@1)Cadd9 (x32030@1)G (320003@1)Cadd9It's (x32030@1)gotta be you, only you
     G (320003@1)Cadd9Only (x32030@1)you

Outro: 
E|-----2-|
B|---3---|
G|-2-----|
D|-------|
A|-------|
E|-------|

D (xx0232@1)G (320003@1)D (xx0232@1)G (320003@1)

They only play that much in the documentary, but to play the whole song the chords are this:

For the intro, verses, pre-chorus and bridge: 
G (320003@1)Cadd9 (x32030@1)G (320003@1)DFor (xx0232@1)the chorus: 
G  Cadd9  G  Cadd9
For the outro: 
D (xx0232@1)G (320003@1)D (xx0232@1)G