Oilpan: make ScrollableAreaTest.ScrollbarTrackAndThumbRepaint work.

third_party/WebKit/Source/platform/scroll/Scrollbar.h

 /*
  * Copyright (C) 2004, 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 30 matching lines @@
 class IntRect;
 class PlatformGestureEvent;
 class PlatformMouseEvent;
 class ScrollAnimatorBase;
 class ScrollableArea;
 class ScrollbarTheme;
 
 class PLATFORM_EXPORT Scrollbar : public Widget, public ScrollbarThemeClient {
 public:
     static PassRefPtrWillBeRawPtr<Scrollbar> create(ScrollableArea*, ScrollbarOrientation, ScrollbarControlSize);
+
+    // Theme object ownership remains with the caller and it must outlive the scrollbar.
     static PassRefPtrWillBeRawPtr<Scrollbar> createForTesting(ScrollableArea*, ScrollbarOrientation, ScrollbarControlSize, ScrollbarTheme*);
 
     ~Scrollbar() override;
 
     // ScrollbarThemeClient implementation.
     int x() const override { return Widget::x(); }
     int y() const override { return Widget::y(); }
     int width() const override { return Widget::width(); }
     int height() const override { return Widget::height(); }
     IntSize size() const override { return Widget::size(); }
@@ skipping 149 matching lines @@
 
     bool m_trackNeedsRepaint;
     bool m_thumbNeedsRepaint;
 };
 
 DEFINE_TYPE_CASTS(Scrollbar, Widget, widget, widget->isScrollbar(), widget.isScrollbar());
 
 } // namespace blink
 
 #endif // Scrollbar_h