content: convert zoom notifications to observer usage

chrome/browser/ui/views/wrench_menu.cc

Index: chrome/browser/ui/views/wrench_menu.cc
diff --git a/chrome/browser/ui/views/wrench_menu.cc b/chrome/browser/ui/views/wrench_menu.cc
index ab5c200f552d99795c0e36c383ec716d2dc0fc7d..1eafa19eb1edfa802ca15ca10016f89e80fec988 100644
--- a/chrome/browser/ui/views/wrench_menu.cc
+++ b/chrome/browser/ui/views/wrench_menu.cc
@@ -481,7 +481,7 @@ static const int kTouchZoomPadding = 14;
 // the zoom, a label showing the current zoom percent, and a button to go
 // full-screen.
 class WrenchMenu::ZoomView : public WrenchMenuView,
-                             public content::NotificationObserver {
+                             public content::HostZoomMap::Observer {
  public:
   ZoomView(WrenchMenu* menu,
            MenuModel* menu_model,
@@ -489,6 +489,8 @@ class WrenchMenu::ZoomView : public WrenchMenuView,
            int increment_index,
            int fullscreen_index)
       : WrenchMenuView(menu, menu_model),
+        content::HostZoomMap::Observer(
+            HostZoomMap::GetForBrowserContext(menu->browser_->profile())),
         fullscreen_index_(fullscreen_index),
         increment_button_(NULL),
         zoom_label_(NULL),
@@ -555,11 +557,6 @@ class WrenchMenu::ZoomView : public WrenchMenuView,
     AddChildView(fullscreen_button_);
 
     UpdateZoomControls();
-
-    registrar_.Add(
-        this, content::NOTIFICATION_ZOOM_LEVEL_CHANGED,
-        content::Source<HostZoomMap>(
-            HostZoomMap::GetForBrowserContext(menu->browser_->profile())));
   }
 
   // Overridden from View.
@@ -613,11 +610,7 @@ class WrenchMenu::ZoomView : public WrenchMenuView,
     }
   }
 
-  // Overridden from content::NotificationObserver.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE {
-    DCHECK_EQ(content::NOTIFICATION_ZOOM_LEVEL_CHANGED, type);
+  virtual void OnZoomLevelChanged(const std::string& host) OVERRIDE {
     UpdateZoomControls();
   }