Strip anonymous blocks when change in style removes need for them

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index 25c4d2a6ee51a933700af5e15b0dabfed9b9ada1..e7d0a624cd4f50502d71b566e11060620fd78bd5 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -328,6 +328,9 @@ void RenderBlock::styleDidChange(StyleDifference diff, const RenderStyle* oldSty
 {
     RenderBox::styleDidChange(diff, oldStyle);
 
+    if (isFloatingOrOutOfFlowPositioned() && oldStyle && !oldStyle->isFloating() && !oldStyle->hasOutOfFlowPosition() && parent() && parent()->isRenderBlockFlow())
+        toRenderBlock(parent())->removeAnonymousWrappersIfRequired();
+
     RenderStyle* newStyle = style();
 
     if (!isAnonymousBlock()) {
@@ -1077,6 +1080,21 @@ static bool canMergeContiguousAnonymousBlocks(RenderObject* oldChild, RenderObje
            && prev->isAnonymousColumnSpanBlock() == next->isAnonymousColumnSpanBlock();
 }
 
+void RenderBlock::removeAnonymousWrappersIfRequired()
+{
+    RenderBox* child = firstChildBox();
+    while (child && (child->isAnonymousBlock() || child->isFloatingOrOutOfFlowPositioned())) {
+        RenderBox* next = child->nextSiblingBox();
+        // A continuation means the wrappers are still required.
+        if (next && next->isRenderBlock() && toRenderBlock(next)->continuation())
+            return;
+        if (child->isAnonymousBlock())
+            collapseAnonymousBlockChild(this, toRenderBlock(child));
+        // |child| may have been destroyed.
+        child = next;
+    }
+}
+
 void RenderBlock::collapseAnonymousBlockChild(RenderBlock* parent, RenderBlock* child)
 {
     // It's possible that this block's destruction may have been triggered by the