support SK_FONTHOST_USES_FONTMGR on mac

src/fonts/SkGScalerContext.cpp

Index: src/fonts/SkGScalerContext.cpp
diff --git a/src/fonts/SkGScalerContext.cpp b/src/fonts/SkGScalerContext.cpp
index ab0dce56870141623a29e3514adc2b0826ca5540..882c70b1214b0750ca0537d3ecafadb36cb559f5 100644
--- a/src/fonts/SkGScalerContext.cpp
+++ b/src/fonts/SkGScalerContext.cpp
@@ -211,6 +211,15 @@ size_t SkGTypeface::onGetTableData(SkFontTableTag tag, size_t offset,
     return fProxy->getTableData(tag, offset, length, data);
 }
 
+SkTypeface* SkGTypeface::onRefMatchingStyle(Style style) const {
+    if (this->style() == style) {
+        return const_cast<SkGTypeface*>(SkRef(this));
+    }
+
+    SkAutoTUnref<SkTypeface> other(fProxy->refMatchingStyle(style));
+    return SkNEW_ARGS(SkGTypeface, (other, fPaint));
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 #if 0