SkPDF: implement xheight for type3 fonts

Change-Id: Ib8e5424e31003798ea141e958a74aa8110ee52c7
Reviewed-on: https://skia-review.googlesource.com/117860
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
2 files changed