Implement Sebastien's overlay scrollbars for native UI (Views).

ui/views/controls/scroll_view_unittest.cc

Index: ui/views/controls/scroll_view_unittest.cc
diff --git a/ui/views/controls/scroll_view_unittest.cc b/ui/views/controls/scroll_view_unittest.cc
index 030bdbbe10a23bccd157239e61f6c75b47669b1b..042347eff52e86ef070b562f5346c6e36f447540 100644
--- a/ui/views/controls/scroll_view_unittest.cc
+++ b/ui/views/controls/scroll_view_unittest.cc
@@ -14,6 +14,7 @@
 #include "ui/views/controls/scrollbar/overlay_scroll_bar.h"
 #include "ui/views/controls/scrollbar/scroll_bar_views.h"
 #include "ui/views/test/test_views.h"
+#include "ui/views/test/views_test_base.h"
 #include "ui/views/test/widget_test.h"
 
 #if defined(OS_MACOSX)
@@ -128,7 +129,7 @@ ui::MouseEvent TestLeftMouseAt(const gfx::Point& location, ui::EventType type) {
 using test::ScrollViewTestApi;
 
 // Simple test harness for testing a ScrollView directly.
-class ScrollViewTest : public testing::Test {
+class ScrollViewTest : public ViewsTestBase {
  public:
   ScrollViewTest() {}