Avoid calling markAncestorsWithChildNeedsStyleRecalc() constantly in childrenChanged

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index d28bed59265c1962b76807d3f69840849f2a0dc2..e2e7961be52671ff16825819f91abf41a4b684f2 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -744,6 +744,9 @@ void Node::markAncestorsWithChildNeedsStyleRecalc()
     for (ContainerNode* p = parentOrShadowHostNode(); p && !p->childNeedsStyleRecalc(); p = p->parentOrShadowHostNode())
         p->setChildNeedsStyleRecalc();
 
+    if (document().hasPendingStyleRecalc())

[ojan, 2014/04/03 16:55:04]

I think this needs a comment explaining why it's here even though it's redundant
with checks in scheduleRenderTreeUpdate. Otherwise someone will look at this
code a year from now and see that this check is redundant and remove it.

+        return;
+
     if (document().needsStyleRecalc() || document().childNeedsStyleRecalc())
         document().scheduleRenderTreeUpdate();
 }