Adding the RemoteSecurityKeyMessageHandler class.

remoting/host/security_key/fake_remote_security_key_ipc_client.h

Index: remoting/host/security_key/fake_remote_security_key_ipc_client.h
diff --git a/remoting/host/security_key/fake_remote_security_key_ipc_client.h b/remoting/host/security_key/fake_remote_security_key_ipc_client.h
index 748597f3cbe909eacb8cbe59fa894e5021f4d100..9734470bbb322bda099c9d53ecabbb76b2cbf3f9 100644
--- a/remoting/host/security_key/fake_remote_security_key_ipc_client.h
+++ b/remoting/host/security_key/fake_remote_security_key_ipc_client.h
@@ -10,6 +10,7 @@
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "remoting/host/security_key/remote_security_key_ipc_client.h"
 
 namespace IPC {
@@ -45,6 +46,8 @@ class FakeRemoteSecurityKeyIpcClient : public RemoteSecurityKeyIpcClient {
   // an IPC channel for testing.
   void SendSecurityKeyRequestViaIpc(const std::string& request_payload);
 
+  base::WeakPtr<FakeRemoteSecurityKeyIpcClient> AsWeakPtr();
+
   const std::string& last_message_received() const {
     return last_message_received_;
   }
@@ -99,6 +102,8 @@ class FakeRemoteSecurityKeyIpcClient : public RemoteSecurityKeyIpcClient {
   // Value returned by SendSecurityKeyRequest() method.
   std::string security_key_response_payload_;
 
+  base::WeakPtrFactory<FakeRemoteSecurityKeyIpcClient> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(FakeRemoteSecurityKeyIpcClient);
 };