Fix SkTypeface::serialize() on Mac by properly indicating local fonts

We used to always set isLocalStream to false in SkTypeface_Mac::onGetFontDescriptor(),
which caused SkTypeface::serialize() to never actually serialize fonts.

BUG=skia:2698
R=reed@google.com, bungeman@google.com

Author: caseq@chromium.org

Review URL: https://codereview.chromium.org/353993003
3 files changed