Switch base::Value typemapping to be by value instead of by unique_ptr.

chrome/utility/extensions/extensions_handler.cc

Index: chrome/utility/extensions/extensions_handler.cc
diff --git a/chrome/utility/extensions/extensions_handler.cc b/chrome/utility/extensions/extensions_handler.cc
index b1567175ccabb7f93adca7420624106924576ce7..f5823075c918206f340e2ffbfef307d648282be7 100644
--- a/chrome/utility/extensions/extensions_handler.cc
+++ b/chrome/utility/extensions/extensions_handler.cc
@@ -73,7 +73,7 @@ class MediaParserImpl : public extensions::mojom::MediaParser {
       metadata::MediaMetadataParser* /* parser */,
       const extensions::api::media_galleries::MediaMetadata& metadata,
       const std::vector<metadata::AttachedImage>& attached_images) {
-    callback.Run(true, metadata.ToValue(), attached_images);
+    callback.Run(true, *metadata.ToValue(), attached_images);
   }
 
   void CheckMediaFile(base::TimeDelta decode_time,