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 b64513cb6bfe9246a2ed77ccfcae0f4e02ba1abd..99dc6c174e960b45ae8dee06dece9b12c4f489cb 100644
--- a/chrome/browser/ui/views/wrench_menu.cc
+++ b/chrome/browser/ui/views/wrench_menu.cc
@@ -480,8 +480,7 @@ static const int kTouchZoomPadding = 14;
 // ZoomView contains the various zoom controls: two buttons to increase/decrease
 // the zoom, a label showing the current zoom percent, and a button to go
 // full-screen.
-class WrenchMenu::ZoomView : public WrenchMenuView,
-                             public content::NotificationObserver {
+class WrenchMenu::ZoomView : public WrenchMenuView {
  public:
   ZoomView(WrenchMenu* menu,
            MenuModel* menu_model,
@@ -495,6 +494,11 @@ class WrenchMenu::ZoomView : public WrenchMenuView,
         decrement_button_(NULL),
         fullscreen_button_(NULL),
         zoom_label_width_(0) {
+    HostZoomMap::GetForBrowserContext(
+        menu_->browser_->profile())->AddZoomLevelChangedCallback(
+            base::Bind(&WrenchMenu::ZoomView::OnZoomLevelChanged,
+                       base::Unretained(this)));
+
     decrement_button_ = CreateButtonWithAccName(
         IDS_ZOOM_MINUS2, MenuButtonBackground::LEFT_BUTTON, decrement_index,
         NULL, IDS_ACCNAME_ZOOM_MINUS2);
@@ -555,11 +559,13 @@ 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())));
+  ~ZoomView() {
+    HostZoomMap::GetForBrowserContext(
+        menu_->browser_->profile())->AddZoomLevelChangedCallback(
+            base::Bind(&WrenchMenu::ZoomView::OnZoomLevelChanged,
+                       base::Unretained(this)));
   }
 
   // Overridden from View.
@@ -613,11 +619,7 @@ 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);
+  void OnZoomLevelChanged(const std::string& host) {
     UpdateZoomControls();
   }