[Refactor] Moved scrollbar creation and deletion to ScrollbarManager

third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp

Index: third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp
index 1f51ca229cdd69df76bb2411d7d12a02d0c7cd74..2971b73dc39ade232fa88f9244c95c414f2625a0 100644
--- a/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintInvalidationCapableScrollableArea.cpp
@@ -280,4 +280,13 @@ void PaintInvalidationCapableScrollableArea::DidScrollWithScrollbar(
   UseCounter::Count(GetLayoutBox()->GetDocument(), scrollbar_use_uma);
 }
 
+bool PaintInvalidationCapableScrollableArea::ShouldUseCustomScrollbars(

[skobes, 2017/06/27 18:48:15]

I think this method would make more sense on LayoutObject, with the name
HasCustomScrollbarStyle.

+    LayoutObject*& style_source) const {

[bokan, 2017/06/27 17:48:52]

This method shouldn't have an output param. The caller should call
LayoutObjectForScrollbars() if needed.

+  DCHECK(!style_source);
+  style_source = LayoutObjectForScrollbars();
+
+  return style_source && style_source->IsBox() &&
+         style_source->StyleRef().HasPseudoStyle(kPseudoIdScrollbar);
+}
+
 }  // namespace blink