[SP] Always paint whole non-custom scrollbars

Source/core/paint/ScrollableAreaPainter.cpp

Index: Source/core/paint/ScrollableAreaPainter.cpp
diff --git a/Source/core/paint/ScrollableAreaPainter.cpp b/Source/core/paint/ScrollableAreaPainter.cpp
index fc21720eea45172f2d09c3e70f013c14e44475c7..d2ba3197894c23924ebd5bc7699fa46b04b245f5 100644
--- a/Source/core/paint/ScrollableAreaPainter.cpp
+++ b/Source/core/paint/ScrollableAreaPainter.cpp
@@ -168,22 +168,27 @@ void ScrollableAreaPainter::paintScrollCorner(GraphicsContext* context, const In
 {
     IntRect absRect = m_scrollableArea.scrollCornerRect();
     absRect.moveBy(paintOffset);
-    if (!absRect.intersects(damageRect))
-        return;
 
     if (m_scrollableArea.scrollCorner()) {
+        if (!absRect.intersects(damageRect))
+            return;
         ScrollbarPainter::paintIntoRect(m_scrollableArea.scrollCorner(), context, paintOffset, LayoutRect(absRect));
         return;
     }
 
-    DrawingRecorder recorder(*context, m_scrollableArea.box(), DisplayItem::ScrollbarCorner, absRect);
-    if (recorder.canUseCachedDrawing())
+    if (!RuntimeEnabledFeatures::slimmingPaintEnabled() && !absRect.intersects(damageRect))
         return;
 
     // We don't want to paint white if we have overlay scrollbars, since we need
     // to see what is behind it.
-    if (!m_scrollableArea.hasOverlayScrollbars())
-        context->fillRect(absRect, Color::white);
+    if (m_scrollableArea.hasOverlayScrollbars())
+        return;
+
+    DrawingRecorder recorder(*context, m_scrollableArea.box(), DisplayItem::ScrollbarCorner, absRect);
+    if (recorder.canUseCachedDrawing())
+        return;
+
+    context->fillRect(absRect, Color::white);
 }
 
 } // namespace blink