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

extensions/utility/utility_handler.cc

Index: extensions/utility/utility_handler.cc
diff --git a/extensions/utility/utility_handler.cc b/extensions/utility/utility_handler.cc
index 4b8e4ac3c7fcbb45b29e93ed737c78a054f766d3..0e85593a4deb73fa59483aa4a74be80dbeae3c5b 100644
--- a/extensions/utility/utility_handler.cc
+++ b/extensions/utility/utility_handler.cc
@@ -63,9 +63,9 @@ class ExtensionUnpackerImpl : public extensions::mojom::ExtensionUnpacker {
     Unpacker unpacker(path.DirName(), path, extension_id, location,
                       creation_flags);
     if (unpacker.Run()) {
-      callback.Run(base::string16(), unpacker.TakeParsedManifest());
+      callback.Run(base::string16(), std::move(*unpacker.TakeParsedManifest()));
     } else {
-      callback.Run(unpacker.error_message(), nullptr);
+      callback.Run(unpacker.error_message(), base::nullopt);
     }
   }