Oilpan: move node/element rare data objects to the heap.

Source/core/animation/ActiveAnimations.h

Index: Source/core/animation/ActiveAnimations.h
diff --git a/Source/core/animation/ActiveAnimations.h b/Source/core/animation/ActiveAnimations.h
index 1a4c0a0bb119a4b2f93e11c8cf203ba90549652f..5f16f8a1d481c583dad754b705e0cd2fdf8e41f6 100644
--- a/Source/core/animation/ActiveAnimations.h
+++ b/Source/core/animation/ActiveAnimations.h
@@ -53,7 +53,6 @@ public:
     }
 
     ~ActiveAnimations();
-    void dispose();
 
     // Animations that are currently active for this element, their effects will be applied
     // during a style recalc. CSS Transitions are included in this stack.
@@ -94,6 +93,14 @@ private:
     // won't be needed once Element and Animation are moved to Oilpan.
     Vector<Animation*> m_animations;
 
+#if ENABLE(OILPAN)
+    // Keep a back reference to the target Element, so that we know

[Erik Corry, 2014/05/05 09:31:27]

Confusing comment.  Having a reference to the element does not ensure it is dead
when we are finalized, only that it is not dead before.

The reason they die together is that there is a strong cycle between the
Element, the ElementRareData and the ActiveAnimations.  But for the oilpan build
it is not necessary that they die together, only that the element lives at least
as long as the animations, which is what this member guarantees.

[sof, 2014/05/05 13:38:58]

Tried to clarify the comment along those lines.

+    // that when this object is finalized, the Element will be dead
+    // too (=> disposing of the above Animations can be done
+    // correctly from our finalizer.)
+    Member<Element> m_target;
+#endif
+
     // CSSAnimations checks if a style change is due to animation.
     friend class CSSAnimations;
 };