Delete final remnants of the buzz namespace.

webrtc/p2p/base/transportchannelimpl.h

Index: webrtc/p2p/base/transportchannelimpl.h
diff --git a/webrtc/p2p/base/transportchannelimpl.h b/webrtc/p2p/base/transportchannelimpl.h
index 1d43e54d0a8fd477e4e0ca700e20f1bcb4f7c67a..7592a3cbc85fe8ea0190ba64538300e202b245ae 100644
--- a/webrtc/p2p/base/transportchannelimpl.h
+++ b/webrtc/p2p/base/transportchannelimpl.h
@@ -16,8 +16,6 @@
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/p2p/base/transportchannel.h"
 
-namespace buzz { class XmlElement; }
-
 namespace webrtc {
 class MetricsObserverInterface;
 }