Identification: Pear - upright shape, small single whites, green roundish leaves, mid-season

I posted these in 2007 as cherries, but they were identified as pear, probably Pyrus calleryana. I'm posting them now in a new thread as cherry look-alikes. The flowers are quite small and the leaves are rather roundish compared with cherry leaves. The bark seems to usually be greyish with whitish splotches.