content: convert zoom notifications to observer usage

chrome/browser/ui/gtk/browser_toolbar_gtk.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_UI_GTK_BROWSER_TOOLBAR_GTK_H_
 #define CHROME_BROWSER_UI_GTK_BROWSER_TOOLBAR_GTK_H_
 
 #include <gtk/gtk.h>
 #include <string>
 
@@ skipping 81 matching lines @@
   // Overridden from MenuGtk::Delegate:
   virtual void StoppedShowing() OVERRIDE;
   virtual GtkIconSet* GetIconSetForId(int idr) OVERRIDE;
   virtual bool AlwaysShowIconForCmd(int command_id) const OVERRIDE;
 
   // Overridden from ui::AcceleratorProvider:
   virtual bool GetAcceleratorForCommandId(
       int id,
       ui::Accelerator* accelerator) OVERRIDE;
 
+  void OnZoomLevelChanged(const std::string& host);
+
   // content::NotificationObserver implementation.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
   // Whether the wrench/hotdogs menu is currently visible to the user.
   bool IsWrenchMenuShowing() const;
 
   // Message that we should react to a state change.
   void UpdateWebContents(content::WebContents* contents,
@@ skipping 105 matching lines @@
   // rendering.
   ui::OwnedWidgetGtk offscreen_entry_;
 
   // Manages the home button drop signal handler.
   scoped_ptr<ui::GtkSignalRegistrar> drop_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserToolbarGtk);
 };
 
 #endif  // CHROME_BROWSER_UI_GTK_BROWSER_TOOLBAR_GTK_H_