Properly register the ulp language_profile pref

The pref was gated on being in the Heuristic Model experiment, which
isn't necessarily the case anymore. The pref should always be registered when
the Heuristic Model is chosen.

Bug: 862229
Change-Id: I41fd77334edac643f43c638a6d56abc408242a53
Reviewed-on: https://chromium-review.googlesource.com/1131814Reviewed-by: Michael Martis <martis@chromium.org>
Commit-Queue: anthonyvd <anthonyvd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574152}

chrome/browser/language/language_model_manager_factory.cc

@@ -83,7 +83,8 @@ content::BrowserContext* LanguageModelManagerFactory::GetBrowserContextToUse(
 
 void LanguageModelManagerFactory::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* const registry) {
-  if (base::FeatureList::IsEnabled(language::kUseHeuristicLanguageModel)) {
+  if (language::GetOverrideLanguageModel() ==
+      language::OverrideLanguageModel::HEURISTIC) {
     registry->RegisterDictionaryPref(
         language::prefs::kUserLanguageProfile,
         user_prefs::PrefRegistrySyncable::SYNCABLE_PRIORITY_PREF);