Build fix after r170811
Build fix after r170811

This CL Just adds #ifdef to V8RecursionScope::m_isolate to fix mac builds.

TBR=esprehn@chromium.org

Review URL: https://codereview.chromium.org/225083002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@170813 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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