Change to std::unique_ptr breaks wtf/DataLog.cpp when DATA_LOG_TO_FILE set to 1
https://bugs.webkit.org/show_bug.cgi?id=122557

Reviewed by Filip Pizlo.

Changed the leakPtr() to release().

* wtf/DataLog.cpp:
(WTF::initializeLogFileOnce):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157176 268f45cc-cd09-0410-ab3c-d52691b4dbfc