Turn on handle zapping for release builds

The impact on performance appears to be negligible, see the golem results on r17004

R=danno@chromium.org

Review URL: https://codereview.chromium.org/25275002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17018 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

build/features.gypi

@@ -109,7 +109,7 @@
       'Release': {
         'variables': {
           'v8_enable_extra_checks%': 0,
-          'v8_enable_handle_zapping%': 0,
+          'v8_enable_handle_zapping%': 1,
         },
         'conditions': [
           ['v8_enable_extra_checks==1', {