Switch HungPluginTabHelper to use WebContentsUserData.

chrome/browser/ui/hung_plugin_tab_helper.h

Index: chrome/browser/ui/hung_plugin_tab_helper.h
diff --git a/chrome/browser/ui/hung_plugin_tab_helper.h b/chrome/browser/ui/hung_plugin_tab_helper.h
index 01795ea790908463f2947fafe06dfa639933d6f1..7e294c12b3e1c0998d4283fe4429dab44b03bf8d 100644
--- a/chrome/browser/ui/hung_plugin_tab_helper.h
+++ b/chrome/browser/ui/hung_plugin_tab_helper.h
@@ -12,6 +12,7 @@
 #include "base/string16.h"
 #include "base/time.h"
 #include "base/timer.h"
+#include "chrome/browser/tab_contents/web_contents_user_data.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_observer.h"
@@ -32,9 +33,9 @@ class InfoBarTabHelper;
 // - Hide the infobar if the plugin starts responding again.
 // - Keep track of all of this for any number of plugins.
 class HungPluginTabHelper : public content::WebContentsObserver,
-                            public content::NotificationObserver {
+                            public content::NotificationObserver,
+                            public WebContentsUserData<HungPluginTabHelper> {
  public:
-  explicit HungPluginTabHelper(content::WebContents* contents);
   virtual ~HungPluginTabHelper();
 
   // content::WebContentsObserver overrides:
@@ -49,6 +50,10 @@ class HungPluginTabHelper : public content::WebContentsObserver,
                        const content::NotificationDetails& details) OVERRIDE;
 
  private:
+  explicit HungPluginTabHelper(content::WebContents* contents);
+  static int kUserDataKey;
+  friend class WebContentsUserData<HungPluginTabHelper>;
+
   class InfoBarDelegate;
   friend class InfoBarDelegate;