- Update ObjectStatsVisitTracker::Visit function to check if CodeCache is of
   CodeCache type, and extract the FixedArray from the struct if so
 - Fix typo in v8-counters.h where count_of_FIXED_ARRAY_XXX fields weren't being
   initialized.

BUG=v8:2780
R=danno@chromium.org, hpayer@chromium.org

Review URL: https://codereview.chromium.org/19257002

Patch from Ross McIlroy <mcilroy@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15748 ce2b1a6d-e550-0410-aec6-3dcde31c8c00