Convert the overlay scrollbar flag to use FeatureList

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index b3b85b4aeb40f375d5a3bf4e76cbc307386d6ee9..d06603494237b28033d45e13bdd3fcbc62112bec 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -97,7 +97,7 @@
 #include "ui/gl/gl_features.h"
 #include "ui/gl/gl_switches.h"
 #include "ui/keyboard/keyboard_switches.h"
-#include "ui/native_theme/native_theme_switches.h"
+#include "ui/native_theme/native_theme_features.h"
 #include "ui/views/views_switches.h"
 
 #if defined(OS_ANDROID)
@@ -1058,9 +1058,7 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kOverlayScrollbarsDescription,
      // Uses the system preference on Mac (a different implementation).
      // On Android, this is always enabled.
-     kOsAura,
-     ENABLE_DISABLE_VALUE_TYPE(switches::kEnableOverlayScrollbar,
-                               switches::kDisableOverlayScrollbar)},
+     kOsAura, FEATURE_VALUE_TYPE(features::kOverlayScrollbar)},
 #endif  // USE_AURA
     {   // See http://crbug.com/120416 for how to remove this flag.
      "save-page-as-mhtml", flag_descriptions::kSavePageAsMhtmlName,