Move code that doesn't depend on PPAPI out of remoting/client/plugin

remoting/client/normalizing_input_filter_mac.h

-// Copyright 2014 The Chromium Authors. All rights reserved.
+// Copyright 2015 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_CLIENT_NORMALIZING_INPUT_FILTER_MAC_H_
+#define REMOTING_CLIENT_NORMALIZING_INPUT_FILTER_MAC_H_
+
 #include <map>
 
 #include "remoting/protocol/input_filter.h"
 
 namespace remoting {
 
 // NormalizingInputFilterMac is designed to solve the problem of missing keyup
 // events on Mac.
 //
 // PROBLEM
@@ skipping 41 matching lines @@
   // Generate keyup events for any keys pressed with CMD.
   void GenerateKeyupEvents();
 
   // A map that stores pressed keycodes and the corresponding key event.
   KeyPressedMap key_pressed_map_;
 
   DISALLOW_COPY_AND_ASSIGN(NormalizingInputFilterMac);
 };
 
 }  // namespace remoting
+
+#endif  // REMOTING_CLIENT_NORMALIZING_INPUT_FILTER_MAC_H_