Prepare for introduction of rtc::PacketTransportInterface.

webrtc/p2p/base/packettransportinterface.h

Index: webrtc/p2p/base/packettransportinterface.h
diff --git a/webrtc/base/optional.cc b/webrtc/p2p/base/packettransportinterface.h
similarity index 61%
copy from webrtc/base/optional.cc
copy to webrtc/p2p/base/packettransportinterface.h
index 6bebdd5a19225fcf46424e97c95d28ccba1b800e..a18081cf72b896a5a1160e08f32e838b9b0b641d 100644
--- a/webrtc/base/optional.cc
+++ b/webrtc/p2p/base/packettransportinterface.h
@@ -8,16 +8,15 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "webrtc/base/optional.h"
+#ifndef WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_
+#define WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_
 
-namespace rtc {
-namespace optional_internal {
-
-#if RTC_HAS_ASAN
+namespace cricket {
+class TransportChannel;
+}
 
-void* FunctionThatDoesNothingImpl(void* x) { return x; }
-
-#endif
+namespace rtc {
+typedef cricket::TransportChannel PacketTransportInterface;
+}
 
-}  // namespace optional_internal
-}  // namespace rtc
+#endif  // WEBRTC_P2P_BASE_PACKETTRANSPORTINTERFACE_H_