When getting the symbols of an object we need to ignore the hidden
properties of the prototype object since the hidden properties are
represented by a single string key and we will not include that hidden
string in the found names.

BUG=350864
LOG=Y
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/192883005

Patch from Erik Arvidsson <arv@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19813 ce2b1a6d-e550-0410-aec6-3dcde31c8c00