remove SkDataSet, and just store a key/value in SkAnnotation

BUG=
R=mtklein@google.com

Review URL: https://codereview.chromium.org/27208002

git-svn-id: http://skia.googlecode.com/svn/trunk/gyp@11759 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/public_headers.gypi b/public_headers.gypi
index f91df37..17253fa 100644
--- a/public_headers.gypi
+++ b/public_headers.gypi
@@ -252,7 +252,6 @@
       'core/SkPreConfig.h',
       'core/SkImageFilterUtils.h',
       'core/SkLineClipper.h',
-      'core/SkDataSet.h',
       'core/SkPathEffect.h',
       'core/SkString.h',
       'core/SkPixelRef.h',