Before finalizing scroll dimensions, check again whether we need scrollbars

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

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 61f17b09b270a1208220efc4096e3eb114cdb1cc..7c659e9bc29de9bea4b616a17eba87691832aba1 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -667,8 +667,8 @@ void PaintLayerScrollableArea::updateScrollDimensions(DoubleSize& scrollOffset,
     }
 
     // overflow:auto may need to lay out again if scrollbars got added/removed.
-    autoHorizontalScrollBarChanged = (box().hasAutoHorizontalScrollbar() && (hasHorizontalScrollbar() != hasHorizontalOverflow)) || (box().style()->overflowX() == OSCROLL && !horizontalScrollbar());
-    autoVerticalScrollBarChanged = (box().hasAutoVerticalScrollbar() && (hasVerticalScrollbar() != hasVerticalOverflow)) || (box().style()->overflowY() == OSCROLL && !verticalScrollbar());
+    autoHorizontalScrollBarChanged |= (box().hasAutoHorizontalScrollbar() && (hasHorizontalScrollbar() != hasHorizontalOverflow)) || (box().style()->overflowX() == OSCROLL && !horizontalScrollbar());
+    autoVerticalScrollBarChanged |= (box().hasAutoVerticalScrollbar() && (hasVerticalScrollbar() != hasVerticalOverflow)) || (box().style()->overflowY() == OSCROLL && !verticalScrollbar());
     if (!visualViewportSuppliesScrollbars() && (autoHorizontalScrollBarChanged || autoVerticalScrollBarChanged)) {
         if (box().hasAutoHorizontalScrollbar())
             setHasHorizontalScrollbar(hasHorizontalOverflow);
@@ -775,8 +775,8 @@ void PaintLayerScrollableArea::finalizeScrollDimensions(const DoubleSize& origin
 void PaintLayerScrollableArea::updateAfterLayout()
 {
     DoubleSize originalScrollOffset;
-    bool autoHorizontalScrollBarChanged;
-    bool autoVerticalScrollBarChanged;
+    bool autoHorizontalScrollBarChanged = false;
+    bool autoVerticalScrollBarChanged = false;
     updateScrollDimensions(originalScrollOffset, autoHorizontalScrollBarChanged, autoVerticalScrollBarChanged);
     finalizeScrollDimensions(originalScrollOffset, autoHorizontalScrollBarChanged, autoVerticalScrollBarChanged);
 }