make pixelsnap textblob* etc gm portable

TBR=reed@google.com

Review URL: https://codereview.chromium.org/1263553002
diff --git a/gm/textblobshader.cpp b/gm/textblobshader.cpp
index 5b9b2e9..bd5ea22 100644
--- a/gm/textblobshader.cpp
+++ b/gm/textblobshader.cpp
@@ -33,6 +33,7 @@
         p.setSubpixelText(true);
         p.setTextSize(30);
         p.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
+        sk_tool_utils::set_portable_typeface(&p);
 
         SkTextBlobBuilder builder;
         int glyphCount = fGlyphs.count();