Add shouldShowParentalControl to help app loadTimeData

The pref was registered and set in https://chromium-review.googlesource.com/c/chromium/src/+/2294861/20/chrome/browser/chromeos/first_run/first_run.cc

Bug: b/159964708
Change-Id: I5daf159e84fa3ec5ce8a70c95098155a199e8f50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321987Reviewed-by: Rachel Carpenter <carpenterr@chromium.org>
Commit-Queue: Zufeng Wang <zufeng@google.com>
Cr-Commit-Position: refs/heads/master@{#792181}

chrome/browser/chromeos/web_applications/chrome_help_app_ui_delegate.cc

@@ -85,6 +85,9 @@ void ChromeHelpAppUIDelegate::PopulateLoadTimeData(
   source->AddBoolean(
       "shouldShowGetStarted",
       pref_service->GetBoolean(prefs::kHelpAppShouldShowGetStarted));
+  source->AddBoolean(
+      "shouldShowParentalControl",
+      pref_service->GetBoolean(prefs::kHelpAppShouldShowParentalControl));
   source->AddBoolean(
       "tabletModeDuringOOBE",
       pref_service->GetBoolean(prefs::kHelpAppTabletModeDuringOobe));