Convert RLZ to a buildflag header

ios/chrome/browser/search_engines/template_url_service_factory.cc

Index: ios/chrome/browser/search_engines/template_url_service_factory.cc
diff --git a/ios/chrome/browser/search_engines/template_url_service_factory.cc b/ios/chrome/browser/search_engines/template_url_service_factory.cc
index 65b0a259a50fa9891380546d14b251674dcafb42..1a95c851f570692e8984b5e83248017fd93ad4f6 100644
--- a/ios/chrome/browser/search_engines/template_url_service_factory.cc
+++ b/ios/chrome/browser/search_engines/template_url_service_factory.cc
@@ -20,8 +20,9 @@
 #include "ios/chrome/browser/search_engines/template_url_service_client_impl.h"
 #include "ios/chrome/browser/search_engines/ui_thread_search_terms_data.h"
 #include "ios/chrome/browser/web_data_service_factory.h"
+#include "rlz/features/features.h"
 
-#if defined(ENABLE_RLZ)
+#if BUILDFLAG(ENABLE_RLZ)
 #include "components/rlz/rlz_tracker.h"  // nogncheck
 #endif
 
@@ -29,7 +30,7 @@ namespace ios {
 namespace {
 
 base::Closure GetDefaultSearchProviderChangedCallback() {
-#if defined(ENABLE_RLZ)
+#if BUILDFLAG(ENABLE_RLZ)
   return base::Bind(base::IgnoreResult(&rlz::RLZTracker::RecordProductEvent),
                     rlz_lib::CHROME, rlz::RLZTracker::ChromeOmnibox(),
                     rlz_lib::SET_TO_GOOGLE);