Add checks to delegate in SigninScreenHandler

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
index f54a0fa6ed0bd316bd3647cf5cce759e82c213e0..4b1e419138ca3296bb92cb89954fa5940529891b 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -301,6 +301,8 @@ void SigninScreenHandler::GetLocalizedStrings(
 }
 
 void SigninScreenHandler::Show(bool oobe_ui) {
+  CHECK(delegate_);
+
   oobe_ui_ = oobe_ui;
   if (!page_is_ready()) {
     show_on_init_ = true;
@@ -324,8 +326,8 @@ void SigninScreenHandler::Show(bool oobe_ui) {
 }
 
 void SigninScreenHandler::SetDelegate(SigninScreenHandlerDelegate* delegate) {
+  CHECK(delegate);
   delegate_ = delegate;
-  DCHECK(delegate_);
   delegate_->SetWebUIHandler(this);
 }