Fix delete of stack allocated object causing test crashes.

Introduced in r8264.

BUG=4173
R=bjornv@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/37959004

Cr-Commit-Position: refs/heads/master@{#8266}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8266 4adac7df-926f-26a2-2b94-8c16560cd09d