Adding the same parameter to the constructors in all subclasses. This change is in preparation for changes to come where this will be needed. BUG=4228 COAUTHOR=kwiberg@webrtc.org R=minyue@webrtc.org Review URL: https://webrtc-codereview.appspot.com/34849004 Cr-Commit-Position: refs/heads/master@{#8210} git-svn-id: http://webrtc.googlecode.com/svn/trunk@8210 4adac7df-926f-26a2-2b94-8c16560cd09d