Convert zoom callbacks to use CallbackRegistry

chrome/browser/ui/gtk/browser_toolbar_gtk.cc

Index: chrome/browser/ui/gtk/browser_toolbar_gtk.cc
diff --git a/chrome/browser/ui/gtk/browser_toolbar_gtk.cc b/chrome/browser/ui/gtk/browser_toolbar_gtk.cc
index ed004becd770de8f9c21cd8f2aa7755ea8586023..a56efe376b78443009ad9e1e38dce5131e339c6f 100644
--- a/chrome/browser/ui/gtk/browser_toolbar_gtk.cc
+++ b/chrome/browser/ui/gtk/browser_toolbar_gtk.cc
@@ -100,9 +100,7 @@ BrowserToolbarGtk::BrowserToolbarGtk(Browser* browser, BrowserWindowGtk* window)
       location_bar_(new LocationBarViewGtk(browser)),
       is_wrench_menu_model_valid_(true),
       browser_(browser),
-      window_(window),
-      zoom_callback_(base::Bind(&BrowserToolbarGtk::OnZoomLevelChanged,
-                                base::Unretained(this))) {
+      window_(window) {
   wrench_menu_model_.reset(new WrenchMenuModel(this, browser_, false));
 
   chrome::AddCommandObserver(browser_, IDC_BACK, this);
@@ -127,9 +125,6 @@ BrowserToolbarGtk::~BrowserToolbarGtk() {
   offscreen_entry_.Destroy();
 
   wrench_menu_.reset();
-
-  HostZoomMap::GetForBrowserContext(
-      browser()->profile())->RemoveZoomLevelChangedCallback(zoom_callback_);
 }
 
 void BrowserToolbarGtk::Init(GtkWindow* top_level_window) {
@@ -246,8 +241,10 @@ void BrowserToolbarGtk::Init(GtkWindow* top_level_window) {
   // The bookmark menu model needs to be able to force the wrench menu to close.
   wrench_menu_model_->bookmark_sub_menu_model()->SetMenuGtk(wrench_menu_.get());
 
-  HostZoomMap::GetForBrowserContext(
-      browser()->profile())->AddZoomLevelChangedCallback(zoom_callback_);
+  zoom_subscription_ = HostZoomMap::GetForBrowserContext(
+      browser()->profile())->AddZoomLevelChangedCallback(
+          base::Bind(&BrowserToolbarGtk::OnZoomLevelChanged,
+                     base::Unretained(this)));
 
   if (ShouldOnlyShowLocation()) {
     gtk_widget_show(event_box_);