0482d01902
This is to fix a race that occurs in unit tests when the tests inherit from the engine class that also implements the callback interface for tracing. If tracing happens while the most derived class is still being constructed, we're in trouble. So, instead, factoring out the TraceCallback implementation. R=pbos@webrtc.org BUG= Review URL: https://webrtc-codereview.appspot.com/43489004 Cr-Commit-Position: refs/heads/master@{#8562} git-svn-id: http://webrtc.googlecode.com/svn/trunk@8562 4adac7df-926f-26a2-2b94-8c16560cd09d