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 110 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 RequestAnimationFrameCallback;
 class ResourceFetcher;
 class SVGDocumentExtensions;
 class SVGUseElement;
@@ skipping 99 matching lines @@
     using ContainerNode::ref;
     using ContainerNode::deref;
 #endif
     using SecurityContext::securityOrigin;
     using SecurityContext::contentSecurityPolicy;
     using TreeScope::getElementById;
 
     virtual bool canContainRangeEndPoint() const override { return true; }
 
     SelectorQueryCache& selectorQueryCache();
+    NthIndexCache* nthIndexCache();
 
     // Focus Management.
     Element* activeElement() const;
     bool hasFocus() const;
 
     // DOM methods & attributes for Document
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(beforecopy);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(beforecut);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(beforepaste);
@@ skipping 794 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; }
 
+    class UseNthIndexCacheScope {
+    public:

[sof, 2015/03/28 08:33:59]

If you add STACK_ALLOCATED(); here and turn the Document& reference into a
RawPtrWillBeMember<Document>, the scope object will be handled as expected
during conservative stack scanning.

(It's a somewhat specialized scope object to expose via Document, so perhaps
consider lifting it out into a separate file?)

[rune, 2015/03/30 09:00:03]

Done.
It only makes sense in the context of Document as it's about temporarily
changing the state of Document, and I wanted to make sure setUseNthIndexCache is
not used by other classes, at least not outside of Document, thus making it a
member class. The alternative would be to make it a friend of Document.

[sof, 2015/03/30 13:27:53]

...
I won't insist, but having the scope object be a friend would look tidier. It
wouldn't be out of place to expose UseNthIndexCacheScope via NthIndexCache.h

+        UseNthIndexCacheScope(Document& document)
+            : m_document(document)
+        {
+            ASSERT(!m_document.useNthIndexCache());
+            m_document.setUseNthIndexCache(true);
+        }
+        ~UseNthIndexCacheScope()
+        {
+            ASSERT(m_document.useNthIndexCache());
+            m_document.setUseNthIndexCache(false);
+        }
+    private:
+        Document& m_document;
+    };
+
 protected:
     Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);
 
     virtual void didUpdateSecurityOrigin() override final;
 
     void clearXMLVersion() { m_xmlVersion = String(); }
 
 #if !ENABLE(OILPAN)
     virtual void dispose() override;
 #endif
@@ skipping 236 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;
+    OwnPtrWillBeMember<NthIndexCache> m_nthIndexCache;

[sof, 2015/03/28 08:33:59]

Add a trace() call for this to Document's trace() implementation.

[rune, 2015/03/30 09:00:03]

Done.

 
     bool m_useSecureKeyboardEntryWhenActive;
 
     DocumentClassFlags m_documentClasses;
 
     bool m_isViewSource;
     bool m_sawElementsInKnownNamespaces;
     bool m_isSrcdocDocument;
     bool m_isMobileDocument;
     bool m_isTransitionDocument;
@@ skipping 60 matching lines @@
     bool m_hasViewportUnits;
 
     using DocumentVisibilityObserverSet = WillBeHeapHashSet<RawPtrWillBeWeakMember<DocumentVisibilityObserver>>;
     DocumentVisibilityObserverSet m_visibilityObservers;
 
     int m_styleRecalcElementCounter;
 
     ParserSynchronizationPolicy m_parserSyncPolicy;
 
     OriginsUsingFeatures::Value m_originsUsingFeaturesValue;
+
+    bool useNthIndexCache() const { return m_useNthIndexCache; }
+    void setUseNthIndexCache(bool);
+
+    bool m_useNthIndexCache;
 };
 
 inline bool Document::shouldOverrideLegacyDescription(ViewportDescription::Type origin)
 {
     // The different (legacy) meta tags have different priorities based on the type
     // regardless of which order they appear in the DOM. The priority is given by the
     // ViewportDescription::Type enum.
     return origin >= m_legacyViewportDescription.type;
 }
 
@@ skipping 27 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