Avoid unnecessary descents into nested boxes with floats.

Source/core/rendering/RenderBlockFlow.cpp

Index: Source/core/rendering/RenderBlockFlow.cpp
diff --git a/Source/core/rendering/RenderBlockFlow.cpp b/Source/core/rendering/RenderBlockFlow.cpp
index e67e947b377957ed25127eac28eb31a433da3bcd..e347c71181cdadb25e860fa21ffaa7ca2b07e985 100644
--- a/Source/core/rendering/RenderBlockFlow.cpp
+++ b/Source/core/rendering/RenderBlockFlow.cpp
@@ -437,6 +437,7 @@ inline bool RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit &
     // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
     computeOverflow(oldClientAfterEdge);
 
+    m_descendantsWithFloatsMarkedForLayout = false;
     return true;
 }
 
@@ -1660,6 +1661,10 @@ void RenderBlockFlow::markAllDescendantsWithFloatsForLayout(RenderBox* floatToRe
     if (!everHadLayout() && !containsFloats())
         return;
 
+    if (m_descendantsWithFloatsMarkedForLayout && !floatToRemove)
+        return;
+    m_descendantsWithFloatsMarkedForLayout |= !floatToRemove;
+
     MarkingBehavior markParents = inLayout ? MarkOnlyThis : MarkContainingBlockChain;
     setChildNeedsLayout(markParents);