Move the following files to content\public\plugin.

content/plugin/content_plugin_client.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 CONTENT_PLUGIN_CONTENT_PLUGIN_CLIENT_H_
-#define CONTENT_PLUGIN_CONTENT_PLUGIN_CLIENT_H_
-#pragma once
-
-#include "base/string16.h"
-#include "content/common/content_client.h"
-
-namespace content {
-
-// Embedder API for participating in plugin logic.
-class ContentPluginClient {
- public:
-  // Notifies that a plugin process has started.
-  virtual void PluginProcessStarted(const string16& plugin_name) = 0;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_PLUGIN_CONTENT_PLUGIN_CLIENT_H_