Move session service and supervised users to buildflags.

chrome/browser/themes/theme_service.h

Index: chrome/browser/themes/theme_service.h
diff --git a/chrome/browser/themes/theme_service.h b/chrome/browser/themes/theme_service.h
index 1f6cde484efa84714790e1b5341d88bc14983db5..2330a07d8f39fdb3101c8424cc500615222aa504 100644
--- a/chrome/browser/themes/theme_service.h
+++ b/chrome/browser/themes/theme_service.h
@@ -17,6 +17,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "build/build_config.h"
+#include "chrome/common/features.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -274,7 +275,7 @@ class ThemeService : public base::NonThreadSafe,
   // case we don't have a theme pack).
   void BuildFromExtension(const extensions::Extension* extension);
 
-#if defined(ENABLE_SUPERVISED_USERS)
+#if BUILDFLAG(ENABLE_SUPERVISED_USERS)
   // Returns true if the profile belongs to a supervised user.
   bool IsSupervisedUser() const;