Make InstallObserver methods not pure-virtual

chrome/browser/ui/app_list/extension_app_model_builder.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/app_list/extension_app_model_builder.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
@@ skipping 166 matching lines @@
     const Extension* extension) {
   if (service_) {
     DVLOG(2) << service_ << ": OnExtensionUninstalled: "
              << extension->id().substr(0, 8);
     service_->RemoveItem(extension->id());
     return;
   }
   model_->DeleteItem(extension->id());
 }
 
-void ExtensionAppModelBuilder::OnAppsReordered() {
-  // Do nothing; App List order does not track extensions order.
-}
-
 void ExtensionAppModelBuilder::OnAppInstalledToAppList(
     const std::string& extension_id) {
   SetHighlightedApp(extension_id);
 }
 
 void ExtensionAppModelBuilder::OnShutdown() {
   if (tracker_) {
     tracker_->RemoveObserver(this);
     tracker_ = NULL;
   }
@@ skipping 110 matching lines @@
     app_list::AppListItem* item = item_list->item_at(idx + 1);
     if (item->GetItemType() == ExtensionAppItem::kItemType) {
       next = static_cast<ExtensionAppItem*>(item);
       break;
     }
   }
   // item->Move will call set_position, overriding the item's position.
   if (prev || next)
     static_cast<ExtensionAppItem*>(item)->Move(prev, next);
 }