Fix scrollbar buttons at hidpi when enable-use-zoom-for-dsf is on.

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

 /*
  * Copyright (c) 2009, Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef ScrollbarThemeAura_h
 #define ScrollbarThemeAura_h
 
+#include "base/gtest_prod_util.h"
 #include "platform/scroll/ScrollbarTheme.h"
 
 namespace blink {
 
 class PLATFORM_EXPORT ScrollbarThemeAura : public ScrollbarTheme {
 public:
     int scrollbarThickness(ScrollbarControlSize) override;
 
 protected:
     bool hasButtons(const ScrollbarThemeClient&) override { return true; }
     bool hasThumb(const ScrollbarThemeClient&) override;
 
     IntRect backButtonRect(const ScrollbarThemeClient&, ScrollbarPart, bool painting = false) override;
     IntRect forwardButtonRect(const ScrollbarThemeClient&, ScrollbarPart, bool painting = false) override;
     IntRect trackRect(const ScrollbarThemeClient&, bool painting = false) override;
     int minimumThumbLength(const ScrollbarThemeClient&) override;
 
     void paintTickmarks(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&) override;
     void paintTrackBackground(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&) override;
     void paintTrackPiece(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&, ScrollbarPart) override;
     void paintButton(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&, ScrollbarPart) override;
     void paintThumb(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&) override;
 
     bool shouldRepaintAllPartsOnInvalidation() const override;
     ScrollbarPart invalidateOnThumbPositionChange(const ScrollbarThemeClient&, float oldPosition, float newPosition) const override;
 
 private:
+    FRIEND_TEST_ALL_PREFIXES(ScrollbarThemeAuraTest, ButtonSizeHorizontal);
+    FRIEND_TEST_ALL_PREFIXES(ScrollbarThemeAuraTest, ButtonSizeVertical);
+
     IntSize buttonSize(const ScrollbarThemeClient&);
 };
 
 } // namespace blink
 
 #endif