Recompute overflow after transform changes

Source/core/rendering/RenderLayerScrollableArea.cpp

Index: Source/core/rendering/RenderLayerScrollableArea.cpp
diff --git a/Source/core/rendering/RenderLayerScrollableArea.cpp b/Source/core/rendering/RenderLayerScrollableArea.cpp
index 3423dbe0830cfdaf512db63854950aeb57af000f..56dc5450ba7797efe986b8fce238df88ddd799ee 100644
--- a/Source/core/rendering/RenderLayerScrollableArea.cpp
+++ b/Source/core/rendering/RenderLayerScrollableArea.cpp
@@ -757,6 +757,26 @@ void RenderLayerScrollableArea::updateAfterCompositingChange()
     layer()->updateScrollingStateAfterCompositingChange();
 }
 
+void RenderLayerScrollableArea::updateAfterOverflowRecalc()
+{
+    computeScrollDimensions();
+    if (Scrollbar* horizontalScrollbar = this->horizontalScrollbar()) {
+        int clientWidth = m_box->pixelSnappedClientWidth();
+        horizontalScrollbar->setProportion(clientWidth, overflowRect().width());
+    }
+    if (Scrollbar* verticalScrollbar = this->verticalScrollbar()) {
+        int clientHeight = m_box->pixelSnappedClientHeight();
+        verticalScrollbar->setProportion(clientHeight, overflowRect().height());
+    }
+
+    bool hasHorizontalOverflow = this->hasHorizontalOverflow();
+    bool hasVerticalOverflow = this->hasVerticalOverflow();
+    bool autoHorizontalScrollBarChanged = m_box->hasAutoHorizontalScrollbar() && (hasHorizontalScrollbar() != hasHorizontalOverflow);
+    bool autoVerticalScrollBarChanged = m_box->hasAutoVerticalScrollbar() && (hasVerticalScrollbar() != hasVerticalOverflow);
+    if (autoHorizontalScrollBarChanged || autoVerticalScrollBarChanged)
+        m_box->setNeedsLayout();
+}
+
 IntSize RenderLayerScrollableArea::clampScrollOffset(const IntSize& scrollOffset) const
 {
     int maxX = scrollWidth() - m_box->pixelSnappedClientWidth();