Add missing SK_API definition at request of Chromium callers

Review URL: https://codereview.appspot.com/6878050

git-svn-id: http://skia.googlecode.com/svn/trunk@6671 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/utils/SkPictureUtils.h b/include/utils/SkPictureUtils.h
index 56318cd..5e6b051 100644
--- a/include/utils/SkPictureUtils.h
+++ b/include/utils/SkPictureUtils.h
@@ -13,7 +13,7 @@
 class SkData;
 struct SkRect;
 
-class SkPictureUtils {
+class SK_API SkPictureUtils {
 public:
     /**
      *  Given a rectangular visible "window" into the picture, return an array