Support libpng 1.6.y

Summary:
This is squashed support including two changes.
  1) a skia image encoder change which can't be upstreamed
     due to skia being removed from the project.

  2) r85181 from trunk which should already be in the AOSP
     project due to import history.

    r85181:
    2011-04-28  ojab  <ojab@ojab.ru>
      Reviewed by David Levin.

      Fix build with libpng-1.5.1
      https://bugs.webkit.org/show_bug.cgi?id=59607

      * platform/image-decoders/png/PNGImageDecoder.cpp:
        (WebCore::readColorProfile):

Test Plan: win

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D375