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

Source/core/dom/MutationObserverRegistration.cpp

Index: Source/core/dom/MutationObserverRegistration.cpp
diff --git a/Source/core/dom/MutationObserverRegistration.cpp b/Source/core/dom/MutationObserverRegistration.cpp
index 12816b0943bc7ef8a243660c0b9450f18fecb2a3..acca5690a54a3d1039c617a7758129937b9e8b6e 100644
--- a/Source/core/dom/MutationObserverRegistration.cpp
+++ b/Source/core/dom/MutationObserverRegistration.cpp
@@ -44,7 +44,7 @@ PassOwnPtrWillBeRawPtr<MutationObserverRegistration> MutationObserverRegistratio
 
 MutationObserverRegistration::MutationObserverRegistration(MutationObserver& observer, Node& registrationNode, MutationObserverOptions options, const HashSet<AtomicString>& attributeFilter)
     : m_observer(observer)
-    , m_registrationNode(registrationNode)
+    , m_registrationNode(&registrationNode)

[Erik Corry, 2014/05/05 14:28:46]

This is called in exactly one place where we have a pointer (this pointer) for
the registration node.  There seems no benefit in having the argument be a
reference, we can just change this and the create() method to use pointers.

[sof, 2014/05/05 15:36:03]

Yes, impedance matching now done.

     , m_options(options)
     , m_attributeFilter(attributeFilter)
 {
@@ -53,15 +53,18 @@ MutationObserverRegistration::MutationObserverRegistration(MutationObserver& obs
 
 MutationObserverRegistration::~MutationObserverRegistration()
 {
-    // dispose() hasn't been called if this assert triggers.
-    ASSERT(!m_observer);
+#if !ENABLE(OILPAN)
+    dispose();
+#endif
 }
 
 void MutationObserverRegistration::dispose()
 {
     clearTransientRegistrations();
-    m_observer->observationEnded(this);
-    m_observer.clear();
+    if (m_observer) {

[Erik Corry, 2014/05/05 14:28:46]

I wonder why we did not need this 'if' before?

[sof, 2014/05/05 14:57:36]

We explicitly dispose() in Node::unregisterMutationObserver() when explicitly
disconnect()ing the observer registrations, as we have to. Which means we will
end up calling dispose() twice for those registration objects in the non-Oilpan
case.

The use of #if in unregisterMutationObserver() was nay'ed in the
MutationObserver CL, but perhaps we should reconsider that?

[Erik Corry, 2014/05/05 14:58:43]

I think it's cool as it is.

[sof, 2014/05/05 15:36:03]

Thinking about it a bit more, it is preferable to do away with the explicit null
check on m_observer here. It avoids having to rediscover that the check is
redundant once the codebase no longer supports both non-Oilpan and Oilpan.

IOW, made the call to dispose() in unregisterMutationObserver() #if-conditional.

+        m_observer->observationEnded(this);
+        m_observer.clear();
+    }
 }
 
 void MutationObserverRegistration::resetObservation(MutationObserverOptions options, const HashSet<AtomicString>& attributeFilter)
@@ -83,7 +86,7 @@ void MutationObserverRegistration::observedSubtreeNodeWillDetach(Node& node)
         m_transientRegistrationNodes = adoptPtr(new NodeHashSet);
 
         ASSERT(!m_registrationNodeKeepAlive);
-        m_registrationNodeKeepAlive = PassRefPtr<Node>(m_registrationNode); // Balanced in clearTransientRegistrations.
+        m_registrationNodeKeepAlive = PassRefPtr<Node>(m_registrationNode.get()); // Balanced in clearTransientRegistrations.
     }
     m_transientRegistrationNodes->add(&node);
 }
@@ -106,7 +109,7 @@ void MutationObserverRegistration::clearTransientRegistrations()
 
 void MutationObserverRegistration::unregister()
 {
-    m_registrationNode.unregisterMutationObserver(this);
+    m_registrationNode->unregisterMutationObserver(this);
     // The above line will cause this object to be deleted, so don't do any more in this function.
 }
 
@@ -116,7 +119,7 @@ bool MutationObserverRegistration::shouldReceiveMutationFrom(Node& node, Mutatio
     if (!(m_options & type))
         return false;
 
-    if (m_registrationNode != node && !isSubtree())
+    if (m_registrationNode != &node && !isSubtree())
         return false;
 
     if (type != MutationObserver::Attributes || !(m_options & MutationObserver::AttributeFilter))
@@ -130,7 +133,7 @@ bool MutationObserverRegistration::shouldReceiveMutationFrom(Node& node, Mutatio
 
 void MutationObserverRegistration::addRegistrationNodesToSet(HashSet<Node*>& nodes) const
 {
-    nodes.add(&m_registrationNode);
+    nodes.add(m_registrationNode.get());
     if (!m_transientRegistrationNodes)
         return;
     for (NodeHashSet::const_iterator iter = m_transientRegistrationNodes->begin(); iter != m_transientRegistrationNodes->end(); ++iter)
@@ -140,6 +143,7 @@ void MutationObserverRegistration::addRegistrationNodesToSet(HashSet<Node*>& nod
 void MutationObserverRegistration::trace(Visitor* visitor)
 {
     visitor->trace(m_observer);
+    visitor->trace(m_registrationNode);
 }
 
 } // namespace WebCore