Fix kMediumQuality invMatrix setup for sizes == mip levels

When downscaling with kMediumQuality in non-clamp mode, if we happen to hit a size == mip level, then SkBitmapProcInfo::init takes the trivial matrix path and doesn't set up a matrix for normalized coords on the assumption that we're going to ignore the transform.  But kMediumQuality disables allow_ignore_fractional_translate, so we take the filter path after all - but with an incorrect matrix.

R=reed@google.com
BUG=chromium:661180
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2476713002

Review-Url: https://codereview.chromium.org/2476713002
2 files changed