MacViews: Use RenderTextHarfBuzz only for Textfields

ui/gfx/render_text_harfbuzz.cc

Index: ui/gfx/render_text_harfbuzz.cc
diff --git a/ui/gfx/render_text_harfbuzz.cc b/ui/gfx/render_text_harfbuzz.cc
index 508655b61bf2c04b773b3ab34014bac55d5511b8..8f0023d9ae5ac4ee20987831fdace2da081db760 100644
--- a/ui/gfx/render_text_harfbuzz.cc
+++ b/ui/gfx/render_text_harfbuzz.cc
@@ -588,6 +588,10 @@ RenderTextHarfBuzz::RenderTextHarfBuzz()
 
 RenderTextHarfBuzz::~RenderTextHarfBuzz() {}
 
+scoped_ptr<RenderText> RenderTextHarfBuzz::NewInstance() const {
+  return scoped_ptr<RenderTextHarfBuzz>(new RenderTextHarfBuzz);
+}
+
 Size RenderTextHarfBuzz::GetStringSize() {
   const SizeF size_f = GetStringSizeF();
   return Size(std::ceil(size_f.width()), size_f.height());