Remove the redundant declaration

content/public/renderer/renderer_ppapi_host.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 CONTENT_PUBLIC_RENDERER_RENDERER_PPAPI_HOST_H_
 #define CONTENT_PUBLIC_RENDERER_RENDERER_PPAPI_HOST_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/platform_file.h"
 #include "base/process.h"
@@ skipping 14 matching lines @@
 struct ChannelHandle;
 }
 
 namespace ppapi {
 class PpapiPermissions;
 namespace host {
 class PpapiHost;
 }
 }
 
-namespace webkit {
-namespace ppapi {
-class PluginInstance;
-}
-}
-
 namespace WebKit {
 class WebPluginContainer;
 }
 
 namespace webkit {
 namespace ppapi {
 class PluginInstance;
 class PluginModule;
 }
 }
@@ skipping 87 matching lines @@
   // Returns true if the plugin is running in process.
   virtual bool IsRunningInProcess() const = 0;
 
  protected:
   virtual ~RendererPpapiHost() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_RENDERER_RENDERER_PPAPI_HOST_H_