Add SK_API for SkData.  Needed for https://bugs.webkit.org/show_bug.cgi?id=91171
Add SK_API for SkData.  Needed for https://bugs.webkit.org/show_bug.cgi?id=91171

Review URL: https://codereview.appspot.com/6420047

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia