SkBitmap::Config is deprecated, use SkColorType

NOTRY=True
BUG=skia:2706

Review URL: https://codereview.chromium.org/379853002

git-svn-id: svn://svn.chromium.org/blink/trunk@177768 bbb929c8-8fbe-4397-9dbb-9b2b20218538