RLSA needsLayout on customscrollbar thickness change.

Source/core/rendering/RenderBox.h

Index: Source/core/rendering/RenderBox.h
diff --git a/Source/core/rendering/RenderBox.h b/Source/core/rendering/RenderBox.h
index 0dc27147f21e9d0e97c9cd9a70a68b0612504eb4..c4329d3fcb89858d37cc46d0f4c08adb93d15499 100644
--- a/Source/core/rendering/RenderBox.h
+++ b/Source/core/rendering/RenderBox.h
@@ -450,6 +450,9 @@ public:
     LayoutUnit availableWidth() const { return style()->isHorizontalWritingMode() ? availableLogicalWidth() : availableLogicalHeight(IncludeMarginBorderPadding); }
     LayoutUnit availableHeight() const { return style()->isHorizontalWritingMode() ? availableLogicalHeight(IncludeMarginBorderPadding) : availableLogicalWidth(); }
 
+    void setCustomScrollbarThicknessChanged(bool thicknessChanged) { m_customScrollbarThicknessChanged = thicknessChanged; }

[skobes, 2014/11/14 03:32:10]

Instead of adding a new boolean, can you put this method in RenderBlock and have
it set m_widthAvailableToChildrenChanged directly?  Also I would suggest calling
it notifyScrollbarThicknessChanged.

You can downcast at the call site, e.g.

if (box->isRenderBlock())
  toRenderBlock(box)->notifyScrollbarThicknessChanged();

I don't think any other subclass of RenderBox would be affected by this.

[MuVen, 2014/11/14 06:10:25]

Done.

+    bool customScrollbarThicknessChanged() const { return m_customScrollbarThicknessChanged; }
+
     virtual int verticalScrollbarWidth() const;
     int horizontalScrollbarHeight() const;
     int instrinsicScrollbarLogicalWidth() const;
@@ -765,6 +768,8 @@ protected:
 
 private:
     OwnPtr<RenderBoxRareData> m_rareData;
+
+    unsigned m_customScrollbarThicknessChanged : 1;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderBox, isBox());