Move enable extensions define to a build flag.

chrome/browser/content_settings/host_content_settings_map_factory.cc

Index: chrome/browser/content_settings/host_content_settings_map_factory.cc
diff --git a/chrome/browser/content_settings/host_content_settings_map_factory.cc b/chrome/browser/content_settings/host_content_settings_map_factory.cc
index f9189fe8cb5ca947d06ebab6c7e7b51db3dc6961..1d0547c23e64dba326b52ae59f19117eccfd3441 100644
--- a/chrome/browser/content_settings/host_content_settings_map_factory.cc
+++ b/chrome/browser/content_settings/host_content_settings_map_factory.cc
@@ -13,8 +13,9 @@
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "components/sync_preferences/pref_service_syncable.h"
 #include "content/public/browser/browser_thread.h"
+#include "extensions/features/features.h"
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "chrome/browser/extensions/extension_service.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/extension_system_provider.h"
@@ -34,7 +35,7 @@ HostContentSettingsMapFactory::HostContentSettingsMapFactory()
 #if BUILDFLAG(ENABLE_SUPERVISED_USERS)
   DependsOn(SupervisedUserSettingsServiceFactory::GetInstance());
 #endif
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   DependsOn(
       extensions::ExtensionsBrowserClient::Get()->GetExtensionSystemFactory());
 #endif
@@ -86,14 +87,14 @@ scoped_refptr<RefcountedKeyedService>
                    settings_map->GetWeakPtr(), true /* after_sync */));
   }
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   ExtensionService *ext_service =
       extensions::ExtensionSystem::Get(profile)->extension_service();
   // This may be null in testing or when the extenion_service hasn't been
   // initialized, in which case it will be registered then.
   if (ext_service)
     ext_service->RegisterContentSettings(settings_map.get());
-#endif // defined(ENABLE_EXTENSIONS)
+#endif // BUILDFLAG(ENABLE_EXTENSIONS)
 #if BUILDFLAG(ENABLE_SUPERVISED_USERS)
   SupervisedUserSettingsService* supervised_service =
       SupervisedUserSettingsServiceFactory::GetForProfile(profile);