content: convert zoom notifications to observer usage

chrome/browser/ui/zoom/zoom_controller.cc

Index: chrome/browser/ui/zoom/zoom_controller.cc
diff --git a/chrome/browser/ui/zoom/zoom_controller.cc b/chrome/browser/ui/zoom/zoom_controller.cc
index 24b33baad649d27d4287532503a79d6d1ad08c83..30271498e29e1e56d36e43c13fa188addf0d37fd 100644
--- a/chrome/browser/ui/zoom/zoom_controller.cc
+++ b/chrome/browser/ui/zoom/zoom_controller.cc
@@ -32,15 +32,23 @@ ZoomController::ZoomController(content::WebContents* web_contents)
                                       base::Unretained(this),
                                       std::string()));
 
-  content::HostZoomMap* zoom_map =
-      content::HostZoomMap::GetForBrowserContext(profile);
-  registrar_.Add(this, content::NOTIFICATION_ZOOM_LEVEL_CHANGED,
-                 content::Source<content::HostZoomMap>(zoom_map));
+  content::HostZoomMap::GetForBrowserContext(
+      web_contents->GetBrowserContext())->AddZoomLevelChangedCallback(
+          base::Bind(&ZoomController::OnZoomLevelChanged,
+                     base::Unretained(this)));
 
   UpdateState(std::string());
 }
 
-ZoomController::~ZoomController() {}
+ZoomController::~ZoomController() {
+  if (!web_contents())
+    return;
+
+  content::HostZoomMap::GetForBrowserContext(
+      web_contents()->GetBrowserContext())->RemoveZoomLevelChangedCallback(
+          base::Bind(&ZoomController::OnZoomLevelChanged,
+                     base::Unretained(this)));

[jam, 2013/01/30 17:50:44]

this doesn't work because the new callback you create here won't be equal to the
one that was used earlier. this class needs to store its callback at
registration, so it can use the same one during unregistration (callbacks are
really just smart pointers, so it's fine to do this)

this comment applies to the other files too

+}
 
 bool ZoomController::IsAtDefaultZoom() const {
   if (!web_contents())
@@ -59,6 +67,10 @@ int ZoomController::GetResourceForZoomLevel() const {
   return zoom > default_zoom_level_.GetValue() ? IDR_ZOOM_PLUS : IDR_ZOOM_MINUS;
 }
 
+void ZoomController::OnZoomLevelChanged(const std::string& host) {
+  UpdateState(host);
+}
+
 void ZoomController::DidNavigateMainFrame(
     const content::LoadCommittedDetails& details,
     const content::FrameNavigateParams& params) {
@@ -67,13 +79,6 @@ void ZoomController::DidNavigateMainFrame(
   UpdateState(std::string());
 }
 
-void ZoomController::Observe(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details) {
-  DCHECK_EQ(content::NOTIFICATION_ZOOM_LEVEL_CHANGED, type);
-  UpdateState(*content::Details<std::string>(details).ptr());
-}
-
 void ZoomController::UpdateState(const std::string& host) {
   // TODO(dbeam): I'm not totally sure why this is happening, and there's been a
   // bit of effort to understand with no tangible results yet. It's possible