Fix LoginScreenStorageCleaner

With our new handling of the pref that handles the force-installed
login screen extensions (https://crrev.com/c/2561847), the
LoginScreenStorageCleaner will be created before the policy is mapped
to its pref. This causes the LoginScreenStorageCleaner to incorrectly
clear all login screen storage entries since it believes that no
extensions are installed.

Simple fix is to remove the call to
ClearPersistentDataForUninstalledExtensions() in its constructor and
only apply this logic when the policy was applied.

Bug: 1157435
Change-Id: Ie8203204c3706e3ffb4b3c0816e2c31e0f9a3036
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2584023Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Alexander Hendrich <hendrich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835641}

chrome/browser/chromeos/login/login_screen_extensions_storage_cleaner.cc

@@ -31,7 +31,6 @@ LoginScreenExtensionsStorageCleaner::LoginScreenExtensionsStorageCleaner() {
       extensions::pref_names::kInstallForceList,
       base::BindRepeating(&LoginScreenExtensionsStorageCleaner::OnPolicyUpdated,
                           base::Unretained(this)));
-  ClearPersistentDataForUninstalledExtensions();
 }
 
 LoginScreenExtensionsStorageCleaner::~LoginScreenExtensionsStorageCleaner() =