Fix the value of the first byte of nal unit generated by fake H.264 encoder. BUG= R=kjellander@webrtc.org, stefan@webrtc.org Review URL: https://webrtc-codereview.appspot.com/38849004 Cr-Commit-Position: refs/heads/master@{#8253} git-svn-id: http://webrtc.googlecode.com/svn/trunk@8253 4adac7df-926f-26a2-2b94-8c16560cd09d