Refactor of Authenticator to allow it to ProcessMessage asynchronously and then call a callback

remoting/protocol/authenticator.h

Index: remoting/protocol/authenticator.h
diff --git a/remoting/protocol/authenticator.h b/remoting/protocol/authenticator.h
index b8aa37d4544220d010195f63a2e89be64f09f126..beb195043c7363480e978ccb4781156e670152f8 100644
--- a/remoting/protocol/authenticator.h
+++ b/remoting/protocol/authenticator.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace buzz {
@@ -83,7 +84,8 @@ class Authenticator {
   // Called in response to incoming message received from the peer.
   // Should only be called when in WAITING_MESSAGE state. Caller
   // retains ownership of |message|.
-  virtual void ProcessMessage(const buzz::XmlElement* message) = 0;
+  virtual void ProcessMessage(const base::Closure& resume_callback,
+                              const buzz::XmlElement* message) = 0;
 
   // Must be called when in MESSAGE_READY state. Returns next
   // authentication message that needs to be sent to the peer.