[win] Add signin support for the app launcher.

ui/app_list/app_list_view_delegate.h

Index: ui/app_list/app_list_view_delegate.h
diff --git a/ui/app_list/app_list_view_delegate.h b/ui/app_list/app_list_view_delegate.h
index a9d73a457f5cb659b8c1a6154c8c6cd47415a157..514354458e20eb1fa20040d4d9f8a8a31a9f1c4d 100644
--- a/ui/app_list/app_list_view_delegate.h
+++ b/ui/app_list/app_list_view_delegate.h
@@ -12,6 +12,7 @@ namespace app_list {
 class AppListItemModel;
 class AppListModel;
 class SearchResult;
+class SigninDelegate;
 
 class APP_LIST_EXPORT AppListViewDelegate {
  public:
@@ -22,6 +23,9 @@ class APP_LIST_EXPORT AppListViewDelegate {
   // Note that AppListView owns the model.
   virtual void SetModel(AppListModel* model) = 0;
 
+  // Gets the SigninDelegate for the app list. Owned by the AppListViewDelegate.
+  virtual SigninDelegate* GetSigninDelegate() = 0;
+
   // Invoked when an AppListeItemModelView is activated by click or enter key.
   virtual void ActivateAppListItem(AppListItemModel* item,
                                    int event_flags) = 0;