Oilpan: move RenderObjects off heap.

Source/core/rendering/svg/RenderSVGResourcePattern.h

Index: Source/core/rendering/svg/RenderSVGResourcePattern.h
diff --git a/Source/core/rendering/svg/RenderSVGResourcePattern.h b/Source/core/rendering/svg/RenderSVGResourcePattern.h
index 22c0973ff9e769602a2fe41188d22ab3317a3208..a9baf4632b9af0c0cce57b4535c02fc1b60aae76 100644
--- a/Source/core/rendering/svg/RenderSVGResourcePattern.h
+++ b/Source/core/rendering/svg/RenderSVGResourcePattern.h
@@ -52,23 +52,31 @@ public:
     static const RenderSVGResourceType s_resourceType = PatternResourceType;
     virtual RenderSVGResourceType resourceType() const override { return s_resourceType; }
 
-    virtual void trace(Visitor*) override;
-
 private:
     PassOwnPtr<PatternData> buildPatternData(const RenderObject&);
     PassRefPtr<const SkPicture> asPicture(const FloatRect& tile, const AffineTransform&) const;
     PatternData* patternForRenderer(const RenderObject&);
 
     bool m_shouldCollectPatternAttributes : 1;
+#if ENABLE(OILPAN)
+    Persistent<PatternAttributesWrapper> m_attributesWrapper;

[haraken, 2015/02/04 05:48:56]

Can we avoid introducing a wrapper by making PatternAttributes not-a-part-of
object in both oilpan and non-oilpan builds?

[sof, 2015/02/04 08:44:32]

That would entail moving the value-based GradientAttributes hierarchy to the
heap and reworking the code that works over it to be imperative. Do we want to
do that & address that here?

[haraken, 2015/02/04 09:25:10]

I thought we can just use OwnPtrWillBePersistent<PatternAttributes> here, but
won't it work?

+
+    PatternAttributes& mutableAttributes() { return m_attributesWrapper->attributes(); }
+    const PatternAttributes& attributes() const { return m_attributesWrapper->attributes(); }
+#else
     PatternAttributes m_attributes;
 
+    PatternAttributes& mutableAttributes() { return m_attributes; }
+    const PatternAttributes& attributes() const { return m_attributes; }
+#endif
+
     // FIXME: we can almost do away with this per-object map, but not quite: the tile size can be
     // relative to the client bounding box, and it gets captured in the cached Pattern shader.
     // Hence, we need one Pattern shader per client. The display list OTOH is the same => we
     // should be able to cache a single display list per RenderSVGResourcePattern + one
     // Pattern(shader) for each client -- this would avoid re-recording when multiple clients
     // share the same pattern.
-    HashMap<const RenderObject*, OwnPtr<PatternData> > m_patternMap;
+    HashMap<const RenderObject*, OwnPtr<PatternData>> m_patternMap;
 };
 
 }