WebRtcVideoFrameTest: Initialize memory to fix DrMemory error

R=pbos@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/41029004

Cr-Commit-Position: refs/heads/master@{#8566}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8566 4adac7df-926f-26a2-2b94-8c16560cd09d
1 file changed