Add the ability to write comments to PNGCodec::Encode.

printing/image.cc

Index: printing/image.cc
diff --git a/printing/image.cc b/printing/image.cc
index 2f5d7e3e89d50e76c4370fd1f0f4d9153813fbe3..425ec6267a1fbc6950d8bdf9c71484c65d4d830a 100644
--- a/printing/image.cc
+++ b/printing/image.cc
@@ -60,10 +60,10 @@ bool Image::SaveToPng(const FilePath& filepath) const {
   std::vector<unsigned char> compressed;
   bool success = gfx::PNGCodec::Encode(&*data_.begin(),
                                        gfx::PNGCodec::FORMAT_BGRA,
-                                       size_.width(),
-                                       size_.height(),
+                                       size_,
                                        row_length_,
                                        true,
+                                       std::vector<gfx::PNGCodec::Comment>(),
                                        &compressed);
   DCHECK(success && compressed.size());
   if (success) {