Object.defineProperty shouldn't be a hint that we're constructing a dictionary.

BUG=362870
LOG=y
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/261583004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21109 ce2b1a6d-e550-0410-aec6-3dcde31c8c00