Cleanup some forward declared structs that are not being used.

chrome/plugin/npobject_proxy.h

 // Copyright (c) 2006-2008 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.
 //
 // A proxy for NPObject that sends all calls to the object to an NPObjectStub
 // running in a different process.
 
 #ifndef CHROME_PLUGIN_NPOBJECT_PROXY_H_
 #define CHROME_PLUGIN_NPOBJECT_PROXY_H_
 
 #include "base/ref_counted.h"
 #include "chrome/common/ipc_channel.h"
 #include "third_party/npapi/bindings/npruntime.h"
 
 class PluginChannelBase;
 struct NPObject;
-struct NPVariant_Param;
 
 namespace base {
 class WaitableEvent;
 }
 
 // When running a plugin in a different process from the renderer, we need to
 // proxy calls to NPObjects across process boundaries.  This happens both ways,
 // as a plugin can get an NPObject for the window, and a page can get an
 // NPObject for the plugin.  In the process that interacts with the NPobject we
 // give it an NPObjectProxy instead.  All calls to it are sent across an IPC
@@ skipping 83 matching lines @@
   static void NPPInvalidate(NPObject *obj);
   static NPClass npclass_proxy_;
 
   int route_id_;
   void* npobject_ptr_;
   scoped_refptr<PluginChannelBase> channel_;
   base::WaitableEvent* modal_dialog_event_;
 };
 
 #endif  // CHROME_PLUGIN_NPOBJECT_PROXY_H_