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 6aab05d6c31015630e53d81b0bf4053e74ad7be2..f4aa9a52970e67d42ea15e0e33bca61816d0ee06 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())

[esprehn, 2014/05/19 20:54:58]

You don't need these nested parens, it's all &&

+        toRenderBlock(parent())->removeAnonymousWrappersIfRequired();
+
     RenderStyle* newStyle = style();
 
     if (!isAnonymousBlock()) {
@@ -1052,6 +1055,21 @@ static bool canMergeContiguousAnonymousBlocks(RenderObject* oldChild, RenderObje
            && prev->isAnonymousColumnSpanBlock() == next->isAnonymousColumnSpanBlock();
 }
 
+void RenderBlock::removeAnonymousWrappersIfRequired()
+{
+    RenderBlock* child = toRenderBlock(firstChildBox());

[esprehn, 2014/05/19 20:54:58]

How do you know this cast is safe?

+    while (child && (child->isAnonymousBlock() || child->isFloatingOrOutOfFlowPositioned())) {
+        RenderBlock* next = toRenderBlock(child->nextSiblingBox());

[esprehn, 2014/05/19 20:54:58]

ditto

+        // A continuation means the wrappers are still required.
+        if (next && next->continuation())
+            return;
+        if (child->isAnonymousBlock())
+            collapseAnonymousBlockChild(this, 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