Fix nhbins calculation.

This regression was introduced by
155bfa7da18cab0d21d87aa2dce4554166836f5d (Normalize size classes.).

Bug: 21326736
(cherry picked from commit c88f3c603be748a424008597bd17cf1e46303532)

Change-Id: I6a5bd95ce95ed464efe916da7d418ad440de4686
1 file changed