Specify clip rects when drawing Mac native widgets

Source/platform/scroll/ScrollbarThemeMacOverlayAPI.mm

Index: Source/platform/scroll/ScrollbarThemeMacOverlayAPI.mm
diff --git a/Source/platform/scroll/ScrollbarThemeMacOverlayAPI.mm b/Source/platform/scroll/ScrollbarThemeMacOverlayAPI.mm
index db6794289f822d3d9b06432c67b173096129ba1e..4b6a0d912e6baaff81bfa0712e73b119ac71729a 100644
--- a/Source/platform/scroll/ScrollbarThemeMacOverlayAPI.mm
+++ b/Source/platform/scroll/ScrollbarThemeMacOverlayAPI.mm
@@ -89,7 +89,7 @@ void ScrollbarThemeMacOverlayAPI::paintTrackBackground(GraphicsContext* context,
 
     GraphicsContextStateSaver stateSaver(*context);
     context->translate(rect.x(), rect.y());
-    LocalCurrentGraphicsContext localContext(context);
+    LocalCurrentGraphicsContext localContext(context, IntRect(IntPoint(), rect.size()));
 
     CGRect frameRect = scrollbar->frameRect();
     ScrollbarPainter scrollbarPainter = painterForScrollbar(scrollbar);
@@ -105,7 +105,7 @@ void ScrollbarThemeMacOverlayAPI::paintThumb(GraphicsContext* context, Scrollbar
 
     GraphicsContextStateSaver stateSaver(*context);
     context->translate(rect.x(), rect.y());
-    LocalCurrentGraphicsContext localContext(context);
+    LocalCurrentGraphicsContext localContext(context, IntRect(IntPoint(), rect.size()));
 
     ScrollbarPainter scrollbarPainter = painterForScrollbar(scrollbar);
     [scrollbarPainter setEnabled:scrollbar->enabled()];