Add support for writing ICC profiles in png encodes

BUG=skia:

Change-Id: I99eb2f157f249ed09d724461ec4a1e31db70816a
Reviewed-on: https://skia-review.googlesource.com/9782
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>
6 files changed