SkPDF: type3: more descriptor values

Also: add fXHeight to SkAdvancedTypefaceMetrics.h

Change-Id: I28314cf93ca9808216ee34c202a0fa9fc2ffe301
Reviewed-on: https://skia-review.googlesource.com/117155
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
diff --git a/src/core/SkAdvancedTypefaceMetrics.h b/src/core/SkAdvancedTypefaceMetrics.h
index db8e697..0ed7de4 100644
--- a/src/core/SkAdvancedTypefaceMetrics.h
+++ b/src/core/SkAdvancedTypefaceMetrics.h
@@ -66,6 +66,7 @@
     int16_t fDescent = 0;      // Max depth below baseline (negative).
     int16_t fStemV = 0;        // Thickness of dominant vertical stem.
     int16_t fCapHeight = 0;    // Height (from baseline) of top of flat capitals.
+    int16_t fXHeight = 0;      // Height (from baseline) of the top of lowercase letter x.
 
     SkIRect fBBox = {0, 0, 0, 0};  // The bounding box of all glyphs (in font units).