content: convert zoom notifications to observer usage

chrome/browser/ui/toolbar/wrench_menu_model.cc

Index: chrome/browser/ui/toolbar/wrench_menu_model.cc
diff --git a/chrome/browser/ui/toolbar/wrench_menu_model.cc b/chrome/browser/ui/toolbar/wrench_menu_model.cc
index 228c7ef63356f2dfb5e0993986d70135f9fd4a23..868b0bf7f75740eeeb60af2a74c130f2cde1d19b 100644
--- a/chrome/browser/ui/toolbar/wrench_menu_model.cc
+++ b/chrome/browser/ui/toolbar/wrench_menu_model.cc
@@ -229,12 +229,13 @@ WrenchMenuModel::WrenchMenuModel(ui::AcceleratorProvider* provider,
   Build(is_new_menu, supports_new_separators);
   UpdateZoomControls();
 
+  HostZoomMap::GetForBrowserContext(
+      browser->profile())->AddZoomLevelChangedCallback(
+          base::Bind(&WrenchMenuModel::OnZoomLevelChanged,
+                     base::Unretained(this)));
+
   tab_strip_model_->AddObserver(this);
 
-  registrar_.Add(
-      this, content::NOTIFICATION_ZOOM_LEVEL_CHANGED,
-      content::Source<HostZoomMap>(
-          HostZoomMap::GetForBrowserContext(browser_->profile())));
   registrar_.Add(this, content::NOTIFICATION_NAV_ENTRY_COMMITTED,
                  content::NotificationService::AllSources());
 }
@@ -242,6 +243,11 @@ WrenchMenuModel::WrenchMenuModel(ui::AcceleratorProvider* provider,
 WrenchMenuModel::~WrenchMenuModel() {
   if (tab_strip_model_)
     tab_strip_model_->RemoveObserver(this);
+
+  HostZoomMap::GetForBrowserContext(
+      browser()->profile())->RemoveZoomLevelChangedCallback(
+          base::Bind(&WrenchMenuModel::OnZoomLevelChanged,
+                     base::Unretained(this)));
 }
 
 bool WrenchMenuModel::DoesCommandIdDismissMenu(int command_id) const {
@@ -452,17 +458,15 @@ void WrenchMenuModel::TabStripModelDeleted() {
   tab_strip_model_ = NULL;
 }
 
+void WrenchMenuModel::OnZoomLevelChanged(const std::string& host) {
+  UpdateZoomControls();
+}
+
 void WrenchMenuModel::Observe(int type,
                               const content::NotificationSource& source,
                               const content::NotificationDetails& details) {
-  switch (type) {
-    case content::NOTIFICATION_ZOOM_LEVEL_CHANGED:
-    case content::NOTIFICATION_NAV_ENTRY_COMMITTED:
-      UpdateZoomControls();
-      break;
-    default:
-      NOTREACHED();
-  }
+  DCHECK(type == content::NOTIFICATION_NAV_ENTRY_COMMITTED);
+  UpdateZoomControls();
 }
 
 // For testing.