[Ash] Hide kiosk apps button when device is disabled

Bug: 1113137
Change-Id: I185e3d91861f9e0b9074d32930ab6735fb054f1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2446054Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Anatoliy Potapchuk <apotapchuk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813606}

ash/shelf/login_shelf_view.cc

@@ -805,8 +805,10 @@ void LoginShelfView::UpdateUi() {
   // Show kiosk apps button if:
   // 1. It's in login screen.
   // 2. There are Kiosk apps available.
+  // 3. Device is not currently blocked.
   kiosk_apps_button_->SetVisible(kiosk_apps_button_->HasApps() &&
-                                 (is_login_primary || is_oobe));
+                                 (is_login_primary || is_oobe) &&
+                                 (dialog_state_ != OobeDialogState::BLOCKING));
   // If there is no visible (and thus focusable) buttons, we shouldn't focus
   // LoginShelfView. We update it here, so we don't need to check visibility
   // every time we move focus to system tray.

ash/shelf/login_shelf_view_unittest.cc

@@ -443,6 +443,7 @@ TEST_F(LoginShelfViewTest, ShouldUpdateUiAfterDialogStateChange) {
 
   // Only Shutdown button should be available if some device blocking
   // screen is shown (e.g. Device Disabled, or Update Required).
+  login_shelf_view_->SetKioskApps(kiosk_apps, {}, {});
   login_shelf_view_->SetLoginDialogState(OobeDialogState::BLOCKING);
   EXPECT_TRUE(ShowsShelfButtons({LoginShelfView::kShutdown}));
 }