Deprecate NonThreadSafe in remoting in favor of SequenceChecker.

remoting/host/host_window.h

 // Copyright 2013 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_HOST_WINDOW_H_
 #define REMOTING_HOST_HOST_WINDOW_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 
 namespace remoting {
 
 class ClientSessionControl;
 
-class HostWindow : public base::NonThreadSafe {
+class HostWindow {
  public:
-  virtual ~HostWindow() {}
+  virtual ~HostWindow();
 
   // Creates a platform-specific instance of the continue window.
   static std::unique_ptr<HostWindow> CreateContinueWindow();
 
   // Creates a platform-specific instance of the disconnect window.
   static std::unique_ptr<HostWindow> CreateDisconnectWindow();
 
   // Starts the UI state machine. |client_session_control| will be used to
   // notify the caller about the local user's actions.
   virtual void Start(
       const base::WeakPtr<ClientSessionControl>& client_session_control) = 0;
 
  protected:
+  // Let |HostWindowProxy| to call DetachFromSequence() when passing an instance
+  // of |HostWindow| to a different sequence.
+  friend class HostWindowProxy;
+
   HostWindow() {}
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
  private:
-  // Let |HostWindowProxy| to call DetachFromThread() when passing an instance
-  // of |HostWindow| to a different thread.
-  friend class HostWindowProxy;
-
   DISALLOW_COPY_AND_ASSIGN(HostWindow);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_HOST_WINDOW_H_