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 a95ad9ee2a5fb8d4cc81f71a43687feab0881aa4..7887b94181c8aa3bc842d7146d722b81ed45ad97 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -331,6 +331,9 @@ 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()) {
@@ -1080,6 +1083,24 @@ static bool canMergeContiguousAnonymousBlocks(RenderObject* oldChild, RenderObje
            && prev->isAnonymousColumnSpanBlock() == next->isAnonymousColumnSpanBlock();
 }
 
+void RenderBlock::removeAnonymousWrappersIfRequired()
+{
+    Vector<RenderBox*, 16> blocksToRemove;

[esprehn, 2014/05/27 21:44:43]

I would ASSERT(isRenderBlockFlow()) here if you expect it to only be called on
those.

+    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
+        // There are still block children in the container, so any anonymous wrappers are still needed.
+        if (!child->isAnonymousBlock() && !child->isFloatingOrOutOfFlowPositioned())
+            return;
+        // We can't remove anonymous wrappers if they contain continuations as this means there are block children present.
+        if (child->isRenderBlock() && toRenderBlock(child)->continuation())
+            return;
+        if (child->isAnonymousBlock())
+            blocksToRemove.append(child);
+    }
+
+    for (size_t i = 0; i < blocksToRemove.size(); i++)
+        collapseAnonymousBlockChild(this, toRenderBlock(blocksToRemove[i]));
+}
+
 void RenderBlock::collapseAnonymousBlockChild(RenderBlock* parent, RenderBlock* child)
 {
     // It's possible that this block's destruction may have been triggered by the