Roll HarfBuzz to 1.3.0

third_party/harfbuzz-ng/src/hb-font-private.hh

Index: third_party/harfbuzz-ng/src/hb-font-private.hh
diff --git a/third_party/harfbuzz-ng/src/hb-font-private.hh b/third_party/harfbuzz-ng/src/hb-font-private.hh
index 8da40a992e963af526a4114d7f3f23d19c7edb80..0b755779490a92c2f46db45d07417b3f1aa4d554 100644
--- a/third_party/harfbuzz-ng/src/hb-font-private.hh
+++ b/third_party/harfbuzz-ng/src/hb-font-private.hh
@@ -505,7 +505,13 @@ struct hb_font_t {
   }
 
   private:
-  inline hb_position_t em_scale (int16_t v, int scale) { return (hb_position_t) (v * (int64_t) scale / face->get_upem ()); }
+  inline hb_position_t em_scale (int16_t v, int scale)
+  {
+    int upem = face->get_upem ();
+    int64_t scaled = v * (int64_t) scale;
+    scaled += scaled >= 0 ? upem/2 : -upem/2; /* Round. */
+    return (hb_position_t) (scaled / upem);
+  }
 };
 
 #define HB_SHAPER_DATA_CREATE_FUNC_EXTRA_ARGS