Change HungPluginTabHelper to listen for infobar changes through Observer style.

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 6cf1a395a86f55ca1a1b4ab39cad98ea133ceec7..1a64b78f3675d49a6f0fcfbf2fe94799b5817e6c 100644
--- a/chrome/browser/ui/hung_plugin_tab_helper.h
+++ b/chrome/browser/ui/hung_plugin_tab_helper.h
@@ -11,8 +11,7 @@
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
+#include "components/infobars/core/infobar_manager.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
@@ -37,8 +36,8 @@ class InfoBarDelegate;
 // - 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 infobars::InfoBarManager::Observer,
+      public content::WebContentsObserver,
       public content::WebContentsUserData<HungPluginTabHelper> {
  public:
   virtual ~HungPluginTabHelper();
@@ -50,11 +49,6 @@ class HungPluginTabHelper
                                        const base::FilePath& plugin_path,
                                        bool is_hung) OVERRIDE;
 
-  // content::NotificationObserver:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
-
   // Called by an infobar when the user selects to kill the plugin.
   void KillPlugin(int child_id);
 
@@ -77,11 +71,18 @@ class HungPluginTabHelper
   // be called even if the bar is not opened, in which case it will do nothing.
   void CloseBar(PluginState* state);
 
-  content::NotificationRegistrar registrar_;
+  // infobars::InfoBarManager::Observer:
+  virtual void OnInfoBarRemoved(infobars::InfoBar* infobar,
+                                bool animate) OVERRIDE;
+  virtual void OnManagerShuttingDown(
+      infobars::InfoBarManager* manager) OVERRIDE;
 
   // All currently hung plugins.
   PluginStateMap hung_plugins_;
 
+  // The number of infobars we are observing.

[Peter Kasting, 2014/05/31 03:44:59]

Nit: We don't actually observe infobars, so how about:

"The number of hung plugin infobars open.  We use this to determine when we
should remove ourselves as an observer of InfoBarManager notifications."

[tfarina, 2014/06/03 03:47:13]

Done.

+  int number_of_infobars_;
+
   DISALLOW_COPY_AND_ASSIGN(HungPluginTabHelper);
 };