Oilpan: Add support of pre-finalization callback to Oilpan infrastructure.

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index d3bc5cf73f62b1ae1a609758caa3d729b47f007e..3bbda6d783a25f32e49b2d8ab12e5066e9477b1c 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -1114,6 +1114,10 @@ void ThreadState::performPendingSweep()
             // Perform thread-specific weak processing.
             while (popAndInvokeWeakPointerCallback(Heap::s_markingVisitor)) { }
         }
+        {
+            TRACE_EVENT0("blink_gc", "ThreadState::invokePreFinalizers");
+            invokePreFinalizers(*Heap::s_markingVisitor);

[haraken, 2014/10/06 01:55:27]

Just to confirm: The main difference between weak callbacks and pre-finalizers
is that pre-finalizers are always called when the target objects die whereas
weak callbacks are not called if the target objects die together with the
observing objects, right? Probably we might want to make the point clearer in
the comment.

+        }
         leaveNoAllocationScope();
 
         // Perform sweeping and finalization.
@@ -1247,6 +1251,25 @@ ThreadState::AttachedThreadStateSet& ThreadState::attachedThreads()
     return threads;
 }
 
+void ThreadState::unregisterPreFinalizerInternal(void* target)
+{
+    if (isSweepInProgress())
+        return;
+    auto it = m_preFinalizers.find(target);
+    ASSERT(it != m_preFinalizers.end());
+    m_preFinalizers.remove(it);
+}
+
+void ThreadState::invokePreFinalizers(Visitor& visitor)
+{
+    Vector<void*> deadObjects;
+    for (auto& entry : m_preFinalizers) {
+        if (entry.value(entry.key, visitor))
+            deadObjects.append(entry.key);
+    }
+    m_preFinalizers.removeAll(deadObjects);
+}
+
 #if ENABLE(GC_PROFILE_MARKING)
 const GCInfo* ThreadState::findGCInfoFromAllThreads(Address address)
 {