Make using WebContentsUserData simpler.

chrome/browser/plugins/plugin_observer.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 CHROME_BROWSER_PLUGINS_PLUGIN_OBSERVER_H_
 #define CHROME_BROWSER_PLUGINS_PLUGIN_OBSERVER_H_
 
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/common/web_contents_user_data.h"
 #include "content/public/browser/web_contents_observer.h"
@@ skipping 21 matching lines @@
                        public WebContentsUserData<PluginObserver> {
  public:
   virtual ~PluginObserver();
 
   // content::WebContentsObserver implementation.
   virtual void PluginCrashed(const FilePath& plugin_path) OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
  private:
   explicit PluginObserver(content::WebContents* web_contents);
-  static int kUserDataKey;
   friend class WebContentsUserData<PluginObserver>;
 
   class PluginPlaceholderHost;
 
 #if defined(ENABLE_PLUGIN_INSTALLATION)
   void InstallMissingPlugin(PluginInstaller* installer,
                             PluginMetadata* plugin_metadata);
 #endif
 
   // Message handlers:
@@ skipping 13 matching lines @@
 
 #if defined(ENABLE_PLUGIN_INSTALLATION)
   // Stores all PluginPlaceholderHosts, keyed by their routing ID.
   std::map<int, PluginPlaceholderHost*> plugin_placeholders_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PluginObserver);
 };
 
 #endif  // CHROME_BROWSER_PLUGINS_PLUGIN_OBSERVER_H_