content: convert zoom notifications to observer usage

chrome/browser/ui/toolbar/wrench_menu_model.h

Index: chrome/browser/ui/toolbar/wrench_menu_model.h
diff --git a/chrome/browser/ui/toolbar/wrench_menu_model.h b/chrome/browser/ui/toolbar/wrench_menu_model.h
index 33992881fb36fbb57cc4ca10f7a3f3e43fc84702..19308acf7596624bfa5eeeaa6cef4be6203584a3 100644
--- a/chrome/browser/ui/toolbar/wrench_menu_model.h
+++ b/chrome/browser/ui/toolbar/wrench_menu_model.h
@@ -8,6 +8,7 @@
 #include "base/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
+#include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/base/accelerators/accelerator.h"
@@ -77,6 +78,7 @@ class WrenchMenuModel : public ui::SimpleMenuModel,
                         public ui::SimpleMenuModel::Delegate,
                         public ui::ButtonMenuItemModel::Delegate,
                         public TabStripModelObserver,
+                        public content::HostZoomMap::Observer,
                         public content::NotificationObserver {
  public:
   // TODO: remove |is_new_menu| and |supports_new_separators|.
@@ -113,6 +115,9 @@ class WrenchMenuModel : public ui::SimpleMenuModel,
                              int index) OVERRIDE;
   virtual void TabStripModelDeleted() OVERRIDE;
 
+  // Overriden from content::HostZoomMap::Observer:
+  virtual void OnZoomLevelChanged(const std::string& host) OVERRIDE;
+
   // Overridden from content::NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,