add a paint-color string to gm/emboss

I'm not hitting SkVMBlitter with a 3D mask
without also implementing support for SkColorShader.

Adding this green "World" tests that path with
a paint color, and should let me test and land 3D
mask support before adding shader support.

Change-Id: I9020a14a8a77dd2946c094308e5ad04beea20068
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/251439
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>

gm/emboss.cpp

@@ -81,6 +81,10 @@ protected:
 
         paint.setStyle(SkPaint::kFill_Style);
         canvas->drawString("Hello", 0, 50, SkFont(nullptr, 50), paint);
+
+        paint.setShader(nullptr);
+        paint.setColor(SK_ColorGREEN);
+        canvas->drawString("World", 0, 100, SkFont(nullptr, 50), paint);
     }
 
 private: