Implement style invalidation tree walk for targeted style recalc upon class change.

Source/core/dom/Node.h

Index: Source/core/dom/Node.h
diff --git a/Source/core/dom/Node.h b/Source/core/dom/Node.h
index 8b4965a07ed5cf164a655850ed5fac17583278fe..cf698b39ff0c6e8352310168f729723a209a7ff1 100644
--- a/Source/core/dom/Node.h
+++ b/Source/core/dom/Node.h
@@ -371,6 +371,13 @@ public:
     void clearChildNeedsDistributionRecalc()  { clearFlag(ChildNeedsDistributionRecalc); }
     void markAncestorsWithChildNeedsDistributionRecalc();
 
+    bool childNeedsStyleInvalidation() const { return getFlag(ChildNeedsStyleInvalidation); }
+    void setChildNeedsStyleInvalidation()  { setFlag(ChildNeedsStyleInvalidation); }
+    void clearChildNeedsStyleInvalidation()  { clearFlag(ChildNeedsStyleInvalidation); }
+    void markAncestorsWithChildNeedsStyleInvalidation();
+    bool needsStyleInvalidation() { return getFlag(NeedsStyleInvalidation); }
+    void setNeedsStyleInvalidation();
+
     void recalcDistribution();
 
     bool shouldNotifyRendererWithIdenticalStyles() const { return getFlag(NotifyRendererWithIdenticalStyles); }
@@ -714,10 +721,13 @@ private:
         CustomElement = 1 << 27,
         CustomElementUpgraded = 1 << 28,
 
+        ChildNeedsStyleInvalidation = 1 << 29,
+        NeedsStyleInvalidation = 1 << 30,
+
         DefaultNodeFlags = IsFinishedParsingChildrenFlag | ChildNeedsStyleRecalcFlag | NeedsReattachStyleChange
     };
 
-    // 4 bits remaining.
+    // 2 bits remaining.
 
     bool getFlag(NodeFlags mask) const { return m_nodeFlags & mask; }
     void setFlag(bool f, NodeFlags mask) const { m_nodeFlags = (m_nodeFlags & ~mask) | (-(int32_t)f & mask); }