Cleanup: Remove unneeded forward declarations from remoting.

remoting/host/register_support_host_request.h

Index: remoting/host/register_support_host_request.h
===================================================================
--- remoting/host/register_support_host_request.h	(revision 109590)
+++ remoting/host/register_support_host_request.h	(working copy)
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef REMOTING_HOST_SUPPORT_HOST_REGISTER_QUERY_H_
-#define REMOTING_HOST_SUPPORT_HOST_REGISTER_QUERY_H_
+#ifndef REMOTING_HOST_REGISTER_SUPPORT_HOST_REQUEST_H_
+#define REMOTING_HOST_REGISTER_SUPPORT_HOST_REQUEST_H_
 
 #include <string>
 
@@ -28,7 +28,6 @@
 
 class IqRequest;
 class IqSender;
-class MutableHostConfig;
 
 // RegisterSupportHostRequest sends support host registeration request
 // to the Chromoting Bot. It listens to the status of the host using
@@ -87,4 +86,4 @@
 
 }  // namespace remoting
 
-#endif  // REMOTING_HOST_SUPPORT_HOST_REGISTER_QUERY_H_
+#endif  // REMOTING_HOST_REGISTER_SUPPORT_HOST_REQUEST_H_