Clean up plug-in placeholders:

chrome/renderer/plugins/plugin_placeholder.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 CHROME_RENDERER_PLUGINS_PLUGIN_PLACEHOLDER_H_
+#define CHROME_RENDERER_PLUGINS_PLUGIN_PLACEHOLDER_H_
+#pragma once
+
+#include "content/public/renderer/render_view_observer.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebPluginParams.h"
+#include "webkit/glue/cpp_bound_class.h"
+#include "webkit/plugins/webview_plugin.h"
+
+namespace webkit {
+struct WebPluginInfo;
+}
+
+// Base class to share code between different plug-in placeholders
+// used in Chrome. Placeholders can be used if a plug-in is missing or not
+// available (blocked or disabled).
+class PluginPlaceholder : public content::RenderViewObserver,
+                          public CppBoundClass,
+                          public webkit::WebViewPlugin::Delegate {
+ protected:
+  // |render_view| and |frame| are weak pointers. If either one is going away,
+  // our |plugin_| will be destroyed as well and will notify us.
+  PluginPlaceholder(content::RenderView* render_view,
+                    WebKit::WebFrame* frame,
+                    const WebKit::WebPluginParams& params,
+                    const std::string& html_data);
+  virtual ~PluginPlaceholder();
+
+  webkit::WebViewPlugin* plugin() { return plugin_; }
+  WebKit::WebFrame* frame() { return frame_; }
+
+  // Can be called by a subclass to replace this placeholder with an actual
+  // plugin from |plugin_info|.
+  void LoadPluginInternal(const webkit::WebPluginInfo& plugin_info);
+
+  // WebViewPlugin::Delegate methods:
+  // Can be called by a subclass to hide this placeholder.
+  void HidePluginInternal();
+
+  virtual void BindWebFrame(WebKit::WebFrame* frame) OVERRIDE;
+  virtual void WillDestroyPlugin() OVERRIDE;
+  virtual void ShowContextMenu(const WebKit::WebMouseEvent& event) OVERRIDE;
+
+ private:
+  WebKit::WebFrame* frame_;
+  WebKit::WebPluginParams plugin_params_;
+  webkit::WebViewPlugin* plugin_;
+
+  DISALLOW_COPY_AND_ASSIGN(PluginPlaceholder);
+};
+
+#endif  // CHROME_RENDERER_PLUGINS_PLUGIN_PLACEHOLDER_H_