The first attempt did not properly handle keyed loads/stores and
did not check the constructors of the objects in the prototype
chain.

Added two more tests to handle the fixed cases.

BUG=v8:1823
TEST=LeakGlobalObjectViaMapKeyed,LeakGlobalContextViaMapProto
Review URL: http://codereview.chromium.org/8974009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10277 ce2b1a6d-e550-0410-aec6-3dcde31c8c00