Add missing SK_API define.

For a detailed explanation of this, please refer to Nico Weber description
here: https://chromiumcodereview.appspot.com/10386108

R=bsalomon@google.com

Review URL: https://codereview.appspot.com/6849075

git-svn-id: http://skia.googlecode.com/svn/trunk@6489 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed