Mac: Don't repaint scrollbars every frame

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

Index: third_party/WebKit/Source/platform/scroll/Scrollbar.h
diff --git a/third_party/WebKit/Source/platform/scroll/Scrollbar.h b/third_party/WebKit/Source/platform/scroll/Scrollbar.h
index 0ec1b88e8a8197190e3287423addafd2e9c8618f..0ed16945fd11bbfc21ddf29325c064f0c4396a3c 100644
--- a/third_party/WebKit/Source/platform/scroll/Scrollbar.h
+++ b/third_party/WebKit/Source/platform/scroll/Scrollbar.h
@@ -140,6 +140,11 @@ public:
     float elasticOverscroll() const override { return m_elasticOverscroll; }
     void setElasticOverscroll(float elasticOverscroll) override { m_elasticOverscroll = elasticOverscroll; }
 
+    bool trackNeedsRepaint() const override { return m_trackNeedsRepaint; }
+    void setTrackNeedsRepaint(bool trackNeedsRepaint) override { m_trackNeedsRepaint = trackNeedsRepaint; }
+    bool thumbNeedsRepaint() const override { return m_thumbNeedsRepaint; }
+    void setThumbNeedsRepaint(bool thumbNeedsRepaint) override { m_thumbNeedsRepaint = thumbNeedsRepaint; }
+
     bool overlapsResizer() const { return m_overlapsResizer; }
     void setOverlapsResizer(bool overlapsResizer) { m_overlapsResizer = overlapsResizer; }
 
@@ -202,6 +207,9 @@ private:
     void invalidateRect(const IntRect&) override { setNeedsPaintInvalidation(); }
 
     float scrollableAreaCurrentPos() const;
+
+    bool m_trackNeedsRepaint;
+    bool m_thumbNeedsRepaint;
 };
 
 DEFINE_TYPE_CASTS(Scrollbar, Widget, widget, widget->isScrollbar(), widget.isScrollbar());