Cache element indices for :nth-child and :nth-last-child selectors.

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 111 matching lines @@
 class LayoutPoint;
 class LiveNodeListBase;
 class Locale;
 class LocalFrame;
 class Location;
 class MainThreadTaskRunner;
 class MediaQueryListListener;
 class MediaQueryMatcher;
 class NodeFilter;
 class NodeIterator;
+class NthIndexCache;
 class Page;
 class PlatformMouseEvent;
 class ProcessingInstruction;
 class QualifiedName;
 class Range;
 class LayoutView;
 class ResourceFetcher;
 class SVGDocumentExtensions;
 class SVGUseElement;
 class ScriptRunner;
@@ skipping 912 matching lines @@
 
     void platformColorsChanged();
 
     virtual DOMTimerCoordinator* timers() override final;
 
     virtual v8::Handle<v8::Object> wrap(v8::Handle<v8::Object> creationContext, v8::Isolate*) override;
     virtual v8::Handle<v8::Object> associateWithWrapper(v8::Isolate*, const WrapperTypeInfo*, v8::Handle<v8::Object> wrapper) override;
 
     OriginsUsingFeatures::Value& originsUsingFeaturesValue() { return m_originsUsingFeaturesValue; }
 
+    NthIndexCache* nthIndexCache() const { return m_nthIndexCache; }
+
 protected:
     Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);
 
     virtual void didUpdateSecurityOrigin() override final;
 
     void clearXMLVersion() { m_xmlVersion = String(); }
 
 #if !ENABLE(OILPAN)
     virtual void dispose() override;
 #endif
 
     virtual PassRefPtrWillBeRawPtr<Document> cloneDocumentWithoutChildren();
 
     bool importContainerNodeChildren(ContainerNode* oldContainerNode, PassRefPtrWillBeRawPtr<ContainerNode> newContainerNode, ExceptionState&);
     void lockCompatibilityMode() { m_compatibilityModeLocked = true; }
     ParserSynchronizationPolicy parserSynchronizationPolicy() const { return m_parserSyncPolicy; }
 
 private:
     friend class IgnoreDestructiveWriteCountIncrementer;
+    friend class NthIndexCache;
 
     bool isDocumentFragment() const = delete; // This will catch anyone doing an unnecessary check.
     bool isDocumentNode() const = delete; // This will catch anyone doing an unnecessary check.
     bool isElementNode() const = delete; // This will catch anyone doing an unnecessary check.
 
     ScriptedAnimationController& ensureScriptedAnimationController();
     virtual SecurityContext& securityContext() override final { return *this; }
     virtual EventQueue* eventQueue() const override final;
 
     // FIXME: Rename the StyleRecalc state to RenderTreeUpdate.
@@ skipping 72 matching lines @@
     bool haveStylesheetsLoaded() const;
 
     void setHoverNode(PassRefPtrWillBeRawPtr<Node>);
     Node* hoverNode() const { return m_hoverNode.get(); }
 
     using EventFactorySet = HashSet<OwnPtr<EventFactoryBase>>;
     static EventFactorySet& eventFactories();
 
     void updateElementOpacity(const AtomicString& cssSelector, double opacity);
 
+    void setNthIndexCache(NthIndexCache* nthIndexCache) { ASSERT(!m_nthIndexCache || !nthIndexCache); m_nthIndexCache = nthIndexCache; }
+
     DocumentLifecycle m_lifecycle;
 
     bool m_hasNodesWithPlaceholderStyle;
     bool m_evaluateMediaQueriesOnStyleRecalc;
 
     // If we do ignore the pending stylesheet count, then we need to add a boolean
     // to track that this happened so that we can do a full repaint when the stylesheets
     // do eventually load.
     PendingSheetLayout m_pendingSheetLayout;
 
@@ skipping 126 matching lines @@
     OwnPtrWillBeMember<SVGDocumentExtensions> m_svgExtensions;
 
     Vector<AnnotatedRegionValue> m_annotatedRegions;
     bool m_hasAnnotatedRegions;
     bool m_annotatedRegionsDirty;
 
     WillBeHeapHashMap<String, RefPtrWillBeMember<HTMLCanvasElement>> m_cssCanvasElements;
 
     OwnPtr<SelectorQueryCache> m_selectorQueryCache;
 
+    // It is safe to keep a raw, untraced pointer to this stack-allocated
+    // cache object: it is set upon the cache object being allocated on
+    // the stack and cleared upon leaving its allocated scope. Hence it
+    // is acceptable not to trace it -- should a conservative GC occur,
+    // the cache object's references will be traced by a stack walk.
+    GC_PLUGIN_IGNORE("461878")
+    NthIndexCache* m_nthIndexCache = nullptr;
+
     bool m_useSecureKeyboardEntryWhenActive;
 
     DocumentClassFlags m_documentClasses;
 
     bool m_isViewSource;
     bool m_sawElementsInKnownNamespaces;
     bool m_isSrcdocDocument;
     bool m_isMobileDocument;
     bool m_isTransitionDocument;
 
@@ skipping 106 matching lines @@
 DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLiveDocumentInstances();
 #endif
 
 #endif // Document_h