Avoid drawing NVPR DIF text when text size is 0

gm/textblobmixedsizes.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 
 #include "Resources.h"
@@ skipping 55 matching lines @@
 
         sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, yOffset);
 
         // micro (will fall out of distance field text even if distance field text is enabled)
         paint.measureText(text, strlen(text), &bounds);
         yOffset += bounds.height();
         paint.setTextSize(14);
 
         sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, yOffset);
 
+        // Zero size.
+        paint.measureText(text, strlen(text), &bounds);
+        yOffset += bounds.height();
+        paint.setTextSize(0);
+
+        sk_tool_utils::add_to_text_blob(&builder, text, paint, 0, yOffset);
+
         // build
         fBlob.reset(builder.build());
     }
 
     SkString onShortName() override {
         SkString name("textblobmixedsizes");
         if (fUseDFT) {
             name.appendf("_df");
         }
         return name;
@@ skipping 96 matching lines @@
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new TextBlobMixedSizes(false); )
 #if SK_SUPPORT_GPU
 DEF_GM( return new TextBlobMixedSizes(true); )
 #endif
 }