content: convert zoom notifications to observer usage

chrome/browser/ui/zoom/zoom_controller.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/zoom/zoom_controller.h"
 
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/common/chrome_notification_types.h"
@@ skipping 14 matching lines @@
     : content::WebContentsObserver(web_contents),
       zoom_percent_(100),
       observer_(NULL) {
   Profile* profile =
       Profile::FromBrowserContext(web_contents->GetBrowserContext());
   default_zoom_level_.Init(prefs::kDefaultZoomLevel, profile->GetPrefs(),
                            base::Bind(&ZoomController::UpdateState,
                                       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())
     return true;
 
   return content::ZoomValuesEqual(web_contents()->GetZoomLevel(),
                                   default_zoom_level_.GetValue());
 }
 
 int ZoomController::GetResourceForZoomLevel() const {
   if (!web_contents())
     return IDR_ZOOM_MINUS;
 
   DCHECK(!IsAtDefaultZoom());
   double zoom = web_contents()->GetZoomLevel();
   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) {
   // If the main frame's content has changed, the new page may have a different
   // zoom level from the old one.
   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
   // that WebContents is NULL as it's being destroyed or some other random
   // reason that I haven't found yet. Applying band-aid. http://crbug.com/144879
   if (!web_contents())
     return;
 
   // If |host| is empty, all observers should be updated.
   if (!host.empty()) {
     // Use the active navigation entry's URL instead of the WebContents' so
     // virtual URLs work (e.g. chrome://settings). http://crbug.com/153950
     content::NavigationEntry* active_entry =
         web_contents()->GetController().GetActiveEntry();
     if (!active_entry ||
         host != net::GetHostOrSpecFromURL(active_entry->GetURL())) {
       return;
     }
   }
 
   bool dummy;
   zoom_percent_ = web_contents()->GetZoomPercent(&dummy, &dummy);
 
   if (observer_)
     observer_->OnZoomChanged(web_contents(), !host.empty());
 }