Optimized implementation of SkMatrix44::preScale
Optimized implementation of SkMatrix44::preScale

preScale() does not need to do a general matrix multiply.  It can do 4x less
arithmetic by directly scaling the columns of the input matrix.
Review URL: https://codereview.appspot.com/6923048

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia