remoting: Cleanup class/struct fwd declarations

remoting/host/basic_desktop_environment.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef REMOTING_HOST_BASIC_DESKTOP_ENVIRONMENT_H_
 #define REMOTING_HOST_BASIC_DESKTOP_ENVIRONMENT_H_
 
 #include <cstdint>
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "remoting/host/desktop_environment.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace webrtc {
 
 class DesktopCaptureOptions;
 
 }  // namespace webrtc
 
 namespace remoting {
 
 // Used to create audio/video capturers and event executor that work with
 // the local console.
@@ skipping 114 matching lines @@
 
   // Used to run UI code.
   scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(BasicDesktopEnvironmentFactory);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_BASIC_DESKTOP_ENVIRONMENT_H_