support SK_FONTHOST_USES_FONTMGR on mac

src/fonts/SkGScalerContext.h

Index: src/fonts/SkGScalerContext.h
diff --git a/src/fonts/SkGScalerContext.h b/src/fonts/SkGScalerContext.h
index b238b0b0a234bb8be20fd2090da98f9fdff0c0e4..1aa1df369e0507fcb37eb51d792d19422807bab9 100644
--- a/src/fonts/SkGScalerContext.h
+++ b/src/fonts/SkGScalerContext.h
@@ -35,6 +35,7 @@ protected:
     virtual int onGetTableTags(SkFontTableTag tags[]) const SK_OVERRIDE;
     virtual size_t onGetTableData(SkFontTableTag, size_t offset,
                                   size_t length, void* data) const SK_OVERRIDE;
+    virtual SkTypeface* onRefMatchingStyle(Style) const SK_OVERRIDE;
 
 private:
     SkTypeface* fProxy;