Revert "Revert "cache SkImage::Info calculation in lazypixelref""

This reverts commit 81eba32ab10f9210c742938819cf1218be5611c9.

ImageDecoder is changed to allow info to be NULL, since it is an output-only parameter.

R=scroggo@google.com

Review URL: https://codereview.chromium.org/33573002

git-svn-id: http://skia.googlecode.com/svn/trunk/src@11896 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed