[iOS] Remove support for asynchronous pref creation.

ios/chrome/browser/application_context_impl.cc

Index: ios/chrome/browser/application_context_impl.cc
diff --git a/ios/chrome/browser/application_context_impl.cc b/ios/chrome/browser/application_context_impl.cc
index 3d42d10d057abbd0fe55d0c1a6fe61ef1d439d92..df2837bb854e0faab1590dcd1e125eced74cfa38 100644
--- a/ios/chrome/browser/application_context_impl.cc
+++ b/ios/chrome/browser/application_context_impl.cc
@@ -198,7 +198,7 @@ void ApplicationContextImpl::CreateLocalState() {
   RegisterLocalStatePrefs(pref_registry.get());
 
   local_state_ = ::CreateLocalState(
-      local_state_path, local_state_task_runner_.get(), pref_registry, false);
+      local_state_path, local_state_task_runner_.get(), pref_registry);
 
   const int max_per_proxy =
       local_state_->GetInteger(ios::prefs::kMaxConnectionsPerProxy);