Handle zero-length encoded images gracefully during deserialization

include/core/SkPicture.h

Index: include/core/SkPicture.h
diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index 774b5424428d2684cbfaa7359090148e4fa09b46..61a584b61d9bd365847713a95b0e0c85a2126b9f 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -103,9 +103,7 @@ public:
 
     /**
      *  Serialize to a stream. If non NULL, serializer will be used to serialize
-     *  any bitmaps in the picture.
-     *
-     *  TODO: Use serializer to serialize SkImages as well.
+     *  bitmaps and images in the picture.

[scroggo, 2015/09/04 18:48:20]

I like that we turn bitmaps into images! I was thinking though, that if we ever
captured an SKP that was created with bitmaps, we might get difference
performance numbers in our tests due to converting to images. Maybe that's okay
though, especially since we are switching to image anyway.

      */
     void serialize(SkWStream*, SkPixelSerializer* = NULL) const;