Make Lacros respect the `EnableSyncConsent` policy

When `EnableSyncConsent` is false, Lacros will now skip the First Run
Experience and enable Sync silently.

Bug: 1324569
Change-Id: Ib828c9f281612bf98ec34cb7ecc9a28ab4fadd3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3643777
Commit-Queue: Nicolas Dossou-Gbété <[email protected]>
Reviewed-by: Igor <[email protected]>
Reviewed-by: David Roger <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1003744}
diff --git a/chrome/browser/prefs/browser_prefs.cc b/chrome/browser/prefs/browser_prefs.cc
index d6c5b01..fee7f37 100644
--- a/chrome/browser/prefs/browser_prefs.cc
+++ b/chrome/browser/prefs/browser_prefs.cc
@@ -1395,6 +1395,8 @@
   certificate_manager::CertificatesHandler::RegisterProfilePrefs(registry);
   policy::PolicyCertService::RegisterProfilePrefs(registry);
   registry->RegisterBooleanPref(prefs::kInsightsExtensionEnabled, false);
+  // By default showing Sync Consent is set to true. It can changed by policy.
+  registry->RegisterBooleanPref(prefs::kEnableSyncConsent, true);
 #if defined(USE_CUPS)
   extensions::PrintingAPIHandler::RegisterProfilePrefs(registry);
 #endif  // defined(USE_CUPS)