add portable and canonical font support for DM

gm/bigtext.cpp

Index: gm/bigtext.cpp
diff --git a/gm/bigtext.cpp b/gm/bigtext.cpp
index 9c2682c15b80a0d0052e8ea70c1318eab4e2bd31..eabad14d0c12d1734973541c444cee8443d070e7 100644
--- a/gm/bigtext.cpp
+++ b/gm/bigtext.cpp
@@ -34,6 +34,7 @@ protected:
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         SkPaint paint;
         paint.setAntiAlias(true);
+        sk_tool_utils::set_portable_typeface(&paint);
         paint.setTextSize(1500);
 
         SkRect r;