Mark Legacy TLS component as USER_VISIBLE

When working on crrev.com/c/1829462, I noticed in manual testing that
the component loading the configuration from disk can take upwards of 6
seconds to complete, causing the configuration to not be loaded by the
time an affected page navigation has completed (causing the UI to not
be shown correctly).

The current version of the TLSDeprecationConfigComponentInstallerPolicy
loads the configuration proto from disk using a PostTask with priority
BEST_EFFORT, causing the configuration load to be delayed, especially
near browser startup. Changing the priority of the load task to
USER_VISIBLE (since the state of the config affects security UI shown
to users) causes this race to go away (or become much, much less likely
to occur, which is sufficient in this case).

Bug: 1011089
Change-Id: Idd98b225a7ae9d6444acf0d8121fa6055f8e06e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1831451
Commit-Queue: Christopher Thompson <cthomp@chromium.org>
Reviewed-by: Sorin Jianu <sorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707171}

chrome/browser/component_updater/tls_deprecation_config_component_installer.cc

@@ -101,7 +101,7 @@ void TLSDeprecationConfigComponentInstallerPolicy::ComponentReady(
   // gave us without checking the default proto from the resource bundle.
   base::PostTaskAndReplyWithResult(
       FROM_HERE,
-      {base::ThreadPool(), base::MayBlock(), base::TaskPriority::BEST_EFFORT},
+      {base::ThreadPool(), base::MayBlock(), base::TaskPriority::USER_VISIBLE},
       base::BindOnce(&LoadTLSDeprecationConfigProtoFromDisk, pb_path),
       base::BindOnce(&SetRemoteTLSDeprecationConfigProto));
 }