Fix a couple of other proxy bugs along the way.
Refactor trap invocation in native code.

R=kmillikin@chromium.org
BUG=v8:1543
TEST=

Review URL: http://codereview.chromium.org/7799026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9312 ce2b1a6d-e550-0410-aec6-3dcde31c8c00