force constrained signed flow in avatar bubble on mac

chrome/browser/ui/cocoa/browser/profile_chooser_controller.mm

Index: chrome/browser/ui/cocoa/browser/profile_chooser_controller.mm
diff --git a/chrome/browser/ui/cocoa/browser/profile_chooser_controller.mm b/chrome/browser/ui/cocoa/browser/profile_chooser_controller.mm
index 0359b92673ad0e39c0e7c2089a8e65abcbbca407..802210850f081dd57fc9657c9e43807a23607064 100644
--- a/chrome/browser/ui/cocoa/browser/profile_chooser_controller.mm
+++ b/chrome/browser/ui/cocoa/browser/profile_chooser_controller.mm
@@ -1000,7 +1000,8 @@ class ActiveProfileObserverBridge : public AvatarMenuObserver,
   webContents_.reset(content::WebContents::Create(
       content::WebContents::CreateParams(browser_->profile())));
   webContents_->GetController().LoadURL(
-      signin::GetPromoURL(source, false),
+      signin::GetPromoURL(
+          source, false /* auto_close */, true /* is_constrained */),
       content::Referrer(),
       content::PAGE_TRANSITION_AUTO_TOPLEVEL,
       std::string());