Only test SVG DM sources against direct raster/gpu sinks.

There isn't much value in testing against indirect or vector sinks.

R=mtklein@google.com,robertphillips@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2252443002

Review-Url: https://codereview.chromium.org/2252443002
diff --git a/dm/DMSrcSink.h b/dm/DMSrcSink.h
index 086becb..0e11633 100644
--- a/dm/DMSrcSink.h
+++ b/dm/DMSrcSink.h
@@ -256,6 +256,7 @@
     Error draw(SkCanvas*) const override;
     SkISize size() const override;
     Name name() const override;
+    bool veto(SinkFlags) const override;
 
 private:
     Path fPath;