Cleanup: Remove unneeded forward declarations in ppapi.

ppapi/proxy/plugin_var_tracker.h

 // Copyright (c) 2011 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 PPAPI_PROXY_PLUGIN_VAR_TRACKER_H_
 #define PPAPI_PROXY_PLUGIN_VAR_TRACKER_H_
 
 #include <map>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/pp_var.h"
 #include "ppapi/proxy/ppapi_proxy_export.h"
 #include "ppapi/shared_impl/var_tracker.h"
 
-struct PPB_Var;
-
 template<typename T> struct DefaultSingletonTraits;
 
 namespace ppapi {
 
 class ProxyObjectVar;
 
 namespace proxy {
 
 class PluginDispatcher;
 
@@ skipping 82 matching lines @@
   typedef std::map<HostVar, int32> HostVarToPluginVarMap;
   HostVarToPluginVarMap host_var_to_plugin_var_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginVarTracker);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_PLUGIN_VAR_TRACKER_H_