Convert utility process extension Unpacker IPC to mojo

extensions/utility/unpacker.h

Index: extensions/utility/unpacker.h
diff --git a/extensions/utility/unpacker.h b/extensions/utility/unpacker.h
index fa77b69fe5566b5f135c2e1e9a1473017fb3d798..63b20be7a06c6b5d8bbd4922606671058fb5c18b 100644
--- a/extensions/utility/unpacker.h
+++ b/extensions/utility/unpacker.h
@@ -53,6 +53,10 @@ class Unpacker {
   base::DictionaryValue* parsed_manifest() { return parsed_manifest_.get(); }
   base::DictionaryValue* parsed_catalogs() { return parsed_catalogs_.get(); }
 
+  std::unique_ptr<base::DictionaryValue> TakeParsedManifest() {
+    return std::move(parsed_manifest_);
+  }
+
  private:
   // Write the decoded images to kDecodedImagesFilename.  We do this instead
   // of sending them over IPC, since they are so large.  Returns true on