Make a test not depend on system settings.

ui/base/test/scoped_preferred_scroller_style_legacy_mac.h

Index: ui/base/test/scoped_preferred_scroller_style_legacy_mac.h
diff --git a/ui/base/test/scoped_preferred_scroller_style_legacy_mac.h b/ui/base/test/scoped_preferred_scroller_style_legacy_mac.h
new file mode 100644
index 0000000000000000000000000000000000000000..99b0028db8fccad760749cb072caa12773280947
--- /dev/null
+++ b/ui/base/test/scoped_preferred_scroller_style_legacy_mac.h
@@ -0,0 +1,36 @@
+// Copyright 2016 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.
+
+#ifndef UI_BASE_TEST_SCOPED_PREFERRED_SCROLLER_STYLE_LEGACY_MAC_H_
+#define UI_BASE_TEST_SCOPED_PREFERRED_SCROLLER_STYLE_LEGACY_MAC_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace base {
+namespace mac {
+class ScopedObjCClassSwizzler;
+}
+}
+
+namespace ui {
+namespace test {
+
+// Overrides system setting for scrollbar style with NSScrollerStyleLegacy,
+// which means "always show scrollbars".
+class ScopedPreferredScrollerStyleLegacy {
+ public:
+  ScopedPreferredScrollerStyleLegacy();
+  ~ScopedPreferredScrollerStyleLegacy();
+
+ private:
+  scoped_ptr<base::mac::ScopedObjCClassSwizzler> swizzler_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedPreferredScrollerStyleLegacy);
+};
+
+}  // namespace test
+}  // namespace ui
+
+#endif  // UI_BASE_TEST_SCOPED_PREFERRED_SCROLLER_STYLE_LEGACY_MAC_H_