We were snapping the top-left of the destination rectangle to integers,
but using the original (fractional) size. This led to us losing rows or
columns of pixels at the first tile boundary.
Also added a GM that demonstrates the bug (now renders correctly).
BUG=skia:
Change-Id: I50629dab9dd90fedad2c7e3393a1b1d1c7a8d45e
Reviewed-on: https://skia-review.googlesource.com/8102
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
a950a86d22