Sibling invalidation sets

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 28bc2ce50ffeb8fcf0eab90ed253b34854c900d3..d518e7982936bed74435576384a083c7683609a3 100644
--- a/Source/core/css/invalidation/InvalidationSet.h
+++ b/Source/core/css/invalidation/InvalidationSet.h
@@ -45,8 +45,8 @@ namespace blink {
 class Element;
 class TracedValue;
 
-// Tracks data to determine which elements of a DOM subtree need to have style
-// recalculated.
+// Tracks data to determine which descendants in a DOM subtree, or
+// siblings and their descendants, need to have style recalculated.
 class CORE_EXPORT InvalidationSet final : public RefCountedWillBeGarbageCollected<InvalidationSet> {
     WTF_MAKE_NONCOPYABLE(InvalidationSet);
 public:
@@ -66,6 +66,10 @@ public:
     void addTagName(const AtomicString& tagName);
     void addAttribute(const AtomicString& attributeLocalName);
 
+    const InvalidationSet* descendants() const { return m_descendantInvalidationSet.get(); }
+
+    InvalidationSet& ensureDescendantInvalidationSet();
+
     void setWholeSubtreeInvalid();
     bool wholeSubtreeInvalid() const { return m_allDescendantsMightBeInvalid; }
 
@@ -81,6 +85,9 @@ public:
     void setCustomPseudoInvalid() { m_customPseudoInvalid = true; }
     bool customPseudoInvalid() const { return m_customPseudoInvalid; }
 
+    unsigned maxDirectAdjacentSelectors() const { return m_maxDirectAdjacentSelectors; }
+    void updateMaxDirectAdjacentSelectors(unsigned value) { m_maxDirectAdjacentSelectors = std::max(value, m_maxDirectAdjacentSelectors); }
+
     bool isEmpty() const { return !m_classes && !m_ids && !m_tagNames && !m_attributes && !m_customPseudoInvalid; }
 
     DECLARE_TRACE();
@@ -119,6 +126,23 @@ private:
 
     // If true, insertion point descendants must be invalidated.
     unsigned m_insertionPointCrossing : 1;
+
+    // Only for sibling invalidation sets, indicates the maximum possible number of siblings affected.
+    unsigned m_maxDirectAdjacentSelectors;

[rune, 2015/10/02 13:17:59]

Can we use sub-classing instead?

SiblingInvalidationSet sub-class which adds these members.

In particular, I think that the code in addFeaturesToInvalidationSets would be
easier to read and understand if you had

class InvalidationSet { ... }

class DescendantInvalidationSet : public InvalidationSet {
    /* nothing added, just to have a separate type to make things clearer */
}

class SiblingInvalidationSet : public InvalidationSet
{
    maxDirectAdjacentSelectors;
    DescendantInvalidationSet m_descendantInvalidationSet
}

[Eric Willigers, 2015/10/14 00:25:40]

Done.

+
+    // Only for sibling invalidation sets, indicates the descendants of siblings.
+    RefPtrWillBeMember<InvalidationSet> m_descendantInvalidationSet;
+
+    friend class RuleFeatureSetTest;
+};
+
+using InvalidationSetVector = WillBeHeapVector<RefPtrWillBeMember<InvalidationSet>>;
+
+struct InvalidationLists {
+    STACK_ALLOCATED();
+
+    InvalidationSetVector descendants;
+    InvalidationSetVector siblings;
 };
 
 } // namespace blink