content: convert zoom notifications to observer usage

content/browser/host_zoom_map_impl.cc

Index: content/browser/host_zoom_map_impl.cc
diff --git a/content/browser/host_zoom_map_impl.cc b/content/browser/host_zoom_map_impl.cc
index 942d6f49c61064c6e06e4d6ff73c30e77ad77360..929d443c90e751b84c1014e5903623d9d87d648c 100644
--- a/content/browser/host_zoom_map_impl.cc
+++ b/content/browser/host_zoom_map_impl.cc
@@ -90,10 +90,8 @@ void HostZoomMapImpl::SetZoomLevel(const std::string& host, double level) {
     }
   }
 
-  NotificationService::current()->Notify(
-      NOTIFICATION_ZOOM_LEVEL_CHANGED,
-      Source<HostZoomMap>(this),
-      Details<const std::string>(&host));
+  FOR_EACH_OBSERVER(HostZoomMap::Observer, observers_,
+                    OnZoomLevelChanged(host));
 }
 
 double HostZoomMapImpl::GetDefaultZoomLevel() const {
@@ -145,11 +143,8 @@ void HostZoomMapImpl::SetTemporaryZoomLevel(int render_process_id,
     }
   }
 
-  std::string host;
-  NotificationService::current()->Notify(
-      NOTIFICATION_ZOOM_LEVEL_CHANGED,
-      Source<HostZoomMap>(this),
-      Details<const std::string>(&host));
+  FOR_EACH_OBSERVER(HostZoomMap::Observer, observers_,
+                    OnZoomLevelChanged(""));
 }
 
 void HostZoomMapImpl::Observe(int type,
@@ -176,6 +171,14 @@ void HostZoomMapImpl::Observe(int type,
   }
 }
 
+void HostZoomMapImpl::AddObserver(HostZoomMap::Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void HostZoomMapImpl::RemoveObserver(HostZoomMap::Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 HostZoomMapImpl::~HostZoomMapImpl() {
 }