add helpers for using SkData with picture serialization

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 0cdb70e933bc3dd6cd30bb15d1ad4a06ac627614..26d90f24606c18087e6621d5acc9a2762cc7f034 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -1428,10 +1428,7 @@ Error ViaSerialization::draw(
     sk_sp<SkPicture> pic(recorder.finishRecordingAsPicture());
 
     // Serialize it and then deserialize it.
-    SkDynamicMemoryWStream wStream;
-    pic->serialize(&wStream);
-    SkAutoTDelete<SkStream> rStream(wStream.detachAsStream());
-    sk_sp<SkPicture> deserialized(SkPicture::MakeFromStream(rStream));
+    sk_sp<SkPicture> deserialized(SkPicture::MakeFromData(pic->serialize().get()));
 
     return draw_to_canvas(fSink, bitmap, stream, log, size, [&](SkCanvas* canvas) {
         canvas->drawPicture(deserialized);