prepare |SVGDocumentExtensions::m_relativeLengthSVGRoots| for oilpan

Source/core/svg/SVGDocumentExtensions.h

 /*
  * Copyright (C) 2006 Apple Inc. All rights reserved.
  * Copyright (C) 2006, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 92 matching lines @@
 #if ENABLE(SVG_FONTS)
     WillBeHeapHashSet<RawPtrWillBeMember<SVGFontFaceElement> > m_svgFontFaceElements;
     // SVGFontFaceElements that are pending and scheduled for removal.
     WillBeHeapHashSet<RefPtrWillBeMember<SVGFontFaceElement> > m_pendingSVGFontFaceElementsForRemoval;
 #endif
     HashMap<AtomicString, RenderSVGResourceContainer*> m_resources;
     HashMap<AtomicString, OwnPtr<SVGPendingElements> > m_pendingResources; // Resources that are pending.
     HashMap<AtomicString, OwnPtr<SVGPendingElements> > m_pendingResourcesForRemoval; // Resources that are pending and scheduled for removal.
     HashMap<SVGElement*, OwnPtr<HashSet<SVGElement*> > > m_elementDependencies;
     OwnPtr<SVGResourcesCache> m_resourcesCache;
-    HashSet<SVGSVGElement*> m_relativeLengthSVGRoots; // Root SVG elements with relative length descendants.
+    WillBeHeapHashSet<RawPtrWillBeWeakMember<SVGSVGElement> > m_relativeLengthSVGRoots; // Root SVG elements with relative length descendants.

[haraken, 2014/06/09 09:37:55]

Just help me understand: How is the weak processing implemented in non-oilpan
builds? I couldn't find code that calls
removeSVGRootWithRelativeLengthDescendents from some SVGSVGElement's destructor.

(It makes sense to make this a hash set of weak members, but I'd like to
understand the background.)

[kouhei (in TOK), 2014/06/09 09:53:46]

if (document is dead && <svg> is dead) the stale ptr in hashset is deleted
anyway
if (document is alive && <svg> is dead) <svg>::removedFrom handles this
if (document is dead && <svg> is alive) the stale ptr in hashset is deleted
anyway 
if (document is alive && <svg> is alive) no need to remove

[kouhei (in TOK), 2014/06/10 05:24:37]

Discussed offline. Made this a strong ref to be explicit that this map never
outlive its referenced elements.

     FloatPoint m_translate;
 #if !ASSERT_DISABLED
     bool m_inRelativeLengthSVGRootsInvalidation;
 #endif
 
 public:
     // This HashMap contains a list of pending resources. Pending resources, are such
     // which are referenced by any object in the SVG document, but do NOT exist yet.
     // For instance, dynamically build gradients / patterns / clippers...
     void addPendingResource(const AtomicString& id, Element*);
@@ skipping 10 matching lines @@
     void markPendingResourcesForRemoval(const AtomicString&);
     Element* removeElementFromPendingResourcesForRemoval(const AtomicString&);
 
 private:
     PassOwnPtr<SVGPendingElements> removePendingResourceForRemoval(const AtomicString&);
 };
 
 }
 
 #endif