Use the same browser instance in the sync confirmation dialog.

chrome/browser/ui/webui/signin/signin_error_handler.cc

Index: chrome/browser/ui/webui/signin/signin_error_handler.cc
diff --git a/chrome/browser/ui/webui/signin/signin_error_handler.cc b/chrome/browser/ui/webui/signin/signin_error_handler.cc
index 4680527565821f724dd384e88f35ae4aac497d4a..bf606bcfca24819857a84a0877fc59e527bd5e33 100644
--- a/chrome/browser/ui/webui/signin/signin_error_handler.cc
+++ b/chrome/browser/ui/webui/signin/signin_error_handler.cc
@@ -70,7 +70,8 @@ void SigninErrorHandler::HandleInitializedWithSize(
   if (duplicate_profile_path_.empty())
     CallJavascriptFunction("signin.error.removeSwitchButton");
 
-  signin::SetInitializedModalHeight(web_ui(), args);
+  signin::SetInitializedModalHeight(signin::GetDesktopBrowser(web_ui()),
+                                    web_ui(), args);
 
   // After the dialog is shown, some platforms might have an element focused.
   // To be consistent, clear the focused element on all platforms.