CSS: Avoid invalidating style when only descendants need updating

Source/core/css/invalidation/InvalidationSet.h

Index: Source/core/css/invalidation/InvalidationSet.h
diff --git a/Source/core/css/invalidation/InvalidationSet.h b/Source/core/css/invalidation/InvalidationSet.h
index fcc8fbc592924058354873997ec069a6a8f84dc8..1c9ed70231b126853c12a5d451da56e08fd9b46c 100644
--- a/Source/core/css/invalidation/InvalidationSet.h
+++ b/Source/core/css/invalidation/InvalidationSet.h
@@ -66,6 +66,9 @@ public:
     void addTagName(const AtomicString& tagName);
     void addAttribute(const AtomicString& attributeLocalName);
 
+    void setAppliesDirectly() { m_appliesDirectly = true; }
+    bool appliesDirectly() const { return m_appliesDirectly; }
+
     void setWholeSubtreeInvalid();
     bool wholeSubtreeInvalid() const { return m_allDescendantsMightBeInvalid; }
 
@@ -102,6 +105,9 @@ private:
     OwnPtrWillBeMember<WillBeHeapHashSet<AtomicString>> m_tagNames;
     OwnPtrWillBeMember<WillBeHeapHashSet<AtomicString>> m_attributes;
 
+    // Indicates the element itself is invalid.

[Timothy Loh, 2015/09/16 04:30:49]

Maybe "must be invalidated" for consistency with other comments

+    unsigned m_appliesDirectly : 1;

[rune, 2015/09/16 08:44:32]

I think there should be a better name, preferably something that includes
"invalidate", but I cannot come up with one that I'm satisfied with.

The other bits are also inconsistently named. We can fix later.

+
     // If true, all descendants might be invalidated, so a full subtree recalc is required.
     unsigned m_allDescendantsMightBeInvalid : 1;