Yes. As the type of second argument of xwalk::application::Manifest class constructor is scoped_ptr, actually the management of  base::DictionaryValue object will be passed to xwalk::application::Manifest

You can see the Pass() function has been called in line162:
+  xwalk::application::Manifest manifest(xwalk::application::Manifest::INVALID_TYPE,
+                                        manifest_dictionary_ptr.Pass());

And the definition of Manifest constructor at line 21 of application/common/manifest.cc:
https://github.com/crosswalk-project/crosswalk/blob/master/application/common/manifest.cc