Fix a crash in PageActionImageView when extensions are reloaded due to incognito settings changing.

chrome/browser/ui/views/location_bar/page_action_image_view.h

Index: chrome/browser/ui/views/location_bar/page_action_image_view.h
===================================================================
--- chrome/browser/ui/views/location_bar/page_action_image_view.h	(revision 107550)
+++ chrome/browser/ui/views/location_bar/page_action_image_view.h	(working copy)
@@ -25,7 +25,8 @@
 class PageActionImageView : public views::ImageView,
                             public ImageLoadingTracker::Observer,
                             public ExtensionContextMenuModel::PopupDelegate,
-                            public ExtensionPopup::Observer {
+                            public ExtensionPopup::Observer,
+                            public content::NotificationObserver {
  public:
   PageActionImageView(LocationBarView* owner,
                       ExtensionAction* page_action);
@@ -58,6 +59,11 @@
   // Overridden from ExtensionPopup::Observer
   virtual void ExtensionPopupIsClosing(ExtensionPopup* popup) OVERRIDE;
 
+  // content::NotificationObserver implementation.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
   // Called to notify the PageAction that it should determine whether to be
   // visible or hidden. |contents| is the TabContents that is active, |url| is
   // the current page URL.
@@ -101,6 +107,8 @@
   // The current popup and the button it came from.  NULL if no popup.
   ExtensionPopup* popup_;
 
+  content::NotificationRegistrar registrar_;
+
   scoped_ptr<views::MenuRunner> menu_runner_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageActionImageView);