CG imagedecoder never sets isOpaque, so add method to SkBitmap to compute that,
and call it from CG imagedecoder.
Review URL: https://codereview.appspot.com/6816101

git-svn-id: http://skia.googlecode.com/svn/trunk@6334 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed