[PDF] Add unpremultiply support and a GM (try3).

This is a resubmit of https://codereview.chromium.org/22831039 which was
reverted because it causes issues on Windows.

BUG=chromium:175548
R=edisonn@google.com

Review URL: https://codereview.chromium.org/29193003

git-svn-id: http://skia.googlecode.com/svn/trunk/gyp@11866 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed