Add the lazy decoder from PictureFlags to SkImageDecoder

R=caryclark@google.com, scroggo@google.com

Author: sglez@google.com

Review URL: https://chromiumcodereview.appspot.com/19109002

git-svn-id: http://skia.googlecode.com/svn/trunk@10111 2bbb7eff-a529-9590-31e7-b0007b416f81
8 files changed