Fix case where install puts two copies of the extension toolbar on the shelf.

chrome/browser/extensions/extension_shelf_model.cc

Index: chrome/browser/extensions/extension_shelf_model.cc
diff --git a/chrome/browser/extensions/extension_shelf_model.cc b/chrome/browser/extensions/extension_shelf_model.cc
index 70013e5dd7236305c0bc559d849e1e8936491d6d..4332b481c667058002513d261bb02116e779ba2f 100644
--- a/chrome/browser/extensions/extension_shelf_model.cc
+++ b/chrome/browser/extensions/extension_shelf_model.cc
@@ -17,8 +17,6 @@
 ExtensionShelfModel::ExtensionShelfModel(Browser* browser)
     : browser_(browser), ready_(false) {
   // Watch extensions loaded and unloaded notifications.
-  registrar_.Add(this, NotificationType::EXTENSION_INSTALLED,
-                 NotificationService::AllSources());
   registrar_.Add(this, NotificationType::EXTENSION_UNLOADED,
                  NotificationService::AllSources());
   registrar_.Add(this, NotificationType::EXTENSIONS_LOADED,
@@ -110,12 +108,6 @@ void ExtensionShelfModel::Observe(NotificationType type,
                                   const NotificationSource& source,
                                   const NotificationDetails& details) {
   switch (type.value) {
-    case NotificationType::EXTENSION_INSTALLED:
-      if (ready_) {
-        AddExtension(Details<Extension>(details).ptr());
-        UpdatePrefs();
-      }
-      break;
     case NotificationType::EXTENSIONS_LOADED:
       if (ready_)
         AddExtensions(Details<ExtensionList>(details).ptr());