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

chrome/browser/extensions/extension_prefs.h

Index: chrome/browser/extensions/extension_prefs.h
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index f02f6ec29e6e03e0e9d6e282bf90061ba900fdc3..828b98b0a15f1c769cf9a352ab1537c1d96e0722 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -251,6 +251,9 @@ class ExtensionPrefs {
   // highest current application launch index found.
   int GetNextAppLaunchIndex();
 
+  // Sets the order the apps should be displayed in the app launcher.
+  void SetAppLauncherOrder(const std::vector<std::string>& extension_ids);
+
   // The extension's update URL data.  If not empty, the ExtensionUpdater
   // will append a ap= parameter to the URL when checking if a new version
   // of the extension is available.