Manual revert of "Convert the overlay scrollbar flag to use FeatureList"

ui/native_theme/native_theme_switches.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/command_line.h"
+#include "ui/native_theme/native_theme_switches.h"
+
+namespace switches {
+
+// Enables or disables overlay scrollbars in Blink (i.e. web content) on Aura
+// or Linux.  The status of native UI overlay scrollbars are determined in
+// PlatformStyle::CreateScrollBar. Does nothing on Mac.
+const char kEnableOverlayScrollbar[] = "enable-overlay-scrollbar";
+const char kDisableOverlayScrollbar[] = "disable-overlay-scrollbar";
+
+}  // namespace switches
+
+namespace ui {
+
+bool IsOverlayScrollbarEnabled() {
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(switches::kDisableOverlayScrollbar))
+    return false;
+
+#if defined(OS_CHROMEOS)
+  return true;
+#else
+  return command_line.HasSwitch(switches::kEnableOverlayScrollbar);
+#endif
+}
+
+}  // namespace ui