Fix the flaky test KioskTest.LaunchAppUserCancel

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 88971eaa06931cc1a1245d12e71b10a0fe8e1226..05092661187b0369729f0a7db5d103911d0206fa 100644
--- a/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/signin_screen_handler.cc
@@ -137,6 +137,24 @@ class CallOnReturn {
   DISALLOW_COPY_AND_ASSIGN(CallOnReturn);
 };
 
+class BoolAutoSet {
+ public:
+  BoolAutoSet(bool* ref, bool val_at_destruct)
+      : bool_ref_(ref),
+        value_at_destruct_(val_at_destruct) {
+  }
+
+  ~BoolAutoSet() {
+    *bool_ref_ = value_at_destruct_;
+  }
+
+ private:
+  bool* bool_ref_;
+  bool value_at_destruct_;
+
+  DISALLOW_COPY_AND_ASSIGN(BoolAutoSet);
+};
+
 }  // namespace
 
 namespace chromeos {
@@ -911,6 +929,8 @@ void SigninScreenHandler::OnUserImageChanged(const user_manager::User& user) {
 }
 
 void SigninScreenHandler::OnPreferencesChanged() {
+  static bool first_preference_changed = true;
+
   // Make sure that one of the login UI is fully functional now, otherwise
   // preferences update would be picked up next time it will be shown.
   if (!webui_visible_) {
@@ -919,17 +939,31 @@ void SigninScreenHandler::OnPreferencesChanged() {
     return;
   }
 
-  // Send the updated user list to the UI.
-  if (delegate_)
-    delegate_->HandleGetUsers();
+  BoolAutoSet at_return_setter(&first_preference_changed, false);
+  preferences_changed_delayed_ = false;
+
+  if (!delegate_)
+    return;
 
-  if (delegate_ && !delegate_->IsShowUsers()) {
+  // Send the updated user list to the UI.
+  delegate_->HandleGetUsers();
+  if (GetCurrentScreen() == OobeScreen::SCREEN_ACCOUNT_PICKER &&
+      delegate_->ShowUsersHasChanged() &&
+      !delegate_->IsShowUsers()) {
+    // We are at the account picker screen and the POD setting has changed
+    // to be disabled. We need to show the add user page.
     HandleShowAddUser(nullptr);
-  } else {
-    UpdateUIState(UI_STATE_ACCOUNT_PICKER, nullptr);
+    return;
   }
 
-  preferences_changed_delayed_ = false;
+  if (delegate_->AllowNewUserChanged() ||
+      (first_preference_changed && !IsSigninScreen(GetCurrentScreen()))) {

[xiyuan, 2016/06/30 20:21:40]

Can we get rid of |first_preference_changed| and use "ui_state_ ==
UI_STATE_UNKNOWN" ?

If that does not work, let's make first_preference_changed a member instead of
local static.

[afakhry, 2016/07/01 13:14:33]

Done.

+    // We need to reload GAIA if it's the very first preference change and the
+    // current screen is neither GAIA not the account picker or the allow new
+    // user setting has changed so that reloaded GAIA shows/hides the option to
+    // create a new account.
+    UpdateUIState(UI_STATE_ACCOUNT_PICKER, nullptr);
+  }
 }
 
 void SigninScreenHandler::ResetSigninScreenHandlerDelegate() {