[NTP] Allow reordering of apps via drag and drop.

chrome/browser/extensions/extension_prefs.cc

 // Copyright (c) 2010 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/extensions/extension_prefs.h"
 
 #include "base/string_util.h"
 #include "base/string_number_conversions.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/extensions/extension_pref_store.h"
@@ skipping 1083 matching lines @@
   int max_value = -1;
   for (DictionaryValue::key_iterator extension_id = extensions->begin_keys();
        extension_id != extensions->end_keys(); ++extension_id) {
     int value = GetAppLaunchIndex(*extension_id);
     if (value > max_value)
       max_value = value;
   }
   return max_value + 1;
 }
 
+void ExtensionPrefs::SetAppLauncherOrder(
+    const std::vector<std::string>& extension_ids) {
+  for (size_t i = 0; i < extension_ids.size(); ++i)
+    SetAppLaunchIndex(extension_ids.at(i), i);
+
+  NotificationService::current()->Notify(
+      NotificationType::EXTENSION_LAUNCHER_REORDERED,
+      Source<ExtensionPrefs>(this),
+      NotificationService::NoDetails());
+}
+
 void ExtensionPrefs::SetUpdateUrlData(const std::string& extension_id,
                                       const std::string& data) {
   DictionaryValue* dictionary = GetExtensionPref(extension_id);
   if (!dictionary) {
     NOTREACHED();
     return;
   }
 
   dictionary->SetString(kUpdateUrlData, data);
   SavePrefsAndNotify();
@@ skipping 186 matching lines @@
 void ExtensionPrefs::RegisterUserPrefs(PrefService* prefs) {
   prefs->RegisterDictionaryPref(kExtensionsPref);
   prefs->RegisterListPref(kExtensionToolbar);
   prefs->RegisterIntegerPref(prefs::kExtensionToolbarSize, -1);
   prefs->RegisterDictionaryPref(kExtensionsBlacklistUpdate);
   prefs->RegisterListPref(prefs::kExtensionInstallAllowList);
   prefs->RegisterListPref(prefs::kExtensionInstallDenyList);
   prefs->RegisterListPref(prefs::kExtensionInstallForceList);
   prefs->RegisterStringPref(kWebStoreLogin, std::string() /* default_value */);
 }