Exclude building signin view controller and its delegate on ChromeOS

chrome/browser/ui/webui/welcome_handler.cc

Index: chrome/browser/ui/webui/welcome_handler.cc
diff --git a/chrome/browser/ui/webui/welcome_handler.cc b/chrome/browser/ui/webui/welcome_handler.cc
index 3ee640ba040cdc8d0e960c2d9679a865876d2877..08c7ac83ed15e449ab4a7505bfb945a9e08f93fd 100644
--- a/chrome/browser/ui/webui/welcome_handler.cc
+++ b/chrome/browser/ui/webui/welcome_handler.cc
@@ -51,8 +51,9 @@ void WelcomeHandler::HandleActivateSignIn(const base::ListValue* args) {
     // them away to the NTP instead.
     GoToNewTabPage();
   } else {
-    GetBrowser()->ShowModalSigninWindow(
-        profiles::BubbleViewMode::BUBBLE_VIEW_MODE_GAIA_SIGNIN,
+    Browser* browser = GetBrowser();
+    browser->signin_view_controller()->ShowModalSignin(
+        profiles::BubbleViewMode::BUBBLE_VIEW_MODE_GAIA_SIGNIN, browser,
         signin_metrics::AccessPoint::ACCESS_POINT_START_PAGE);
   }
 }