Refactor the Heap into ThreadHeap to prepare for per thread heaps

third_party/WebKit/Source/platform/heap/PersistentNode.cpp

Index: third_party/WebKit/Source/platform/heap/PersistentNode.cpp
diff --git a/third_party/WebKit/Source/platform/heap/PersistentNode.cpp b/third_party/WebKit/Source/platform/heap/PersistentNode.cpp
index abd7a1264515f10cbda31c100d1ff52405b54007..6c6923fc2a8c84b4c7a3590f18effa2483ea8dfa 100644
--- a/third_party/WebKit/Source/platform/heap/PersistentNode.cpp
+++ b/third_party/WebKit/Source/platform/heap/PersistentNode.cpp
@@ -49,7 +49,7 @@ void PersistentRegion::ensurePersistentNodeSlots(void* self, TraceCallback trace
 // a PersistentNodeSlot that contains only freed PersistentNodes,
 // we delete the PersistentNodeSlot. This function rebuilds the free
 // list of PersistentNodes.
-void PersistentRegion::tracePersistentNodes(Visitor* visitor)
+void PersistentRegion::tracePersistentNodes(Visitor* visitor, bool (*shouldTrace)(Visitor*, PersistentNode*))
 {
     m_freeListHead = nullptr;
     int persistentCount = 0;
@@ -68,6 +68,8 @@ void PersistentRegion::tracePersistentNodes(Visitor* visitor)
                 freeListNext = node;
                 ++freeCount;
             } else {
+                if (shouldTrace && !shouldTrace(visitor, node))
+                    return;

[haraken, 2016/01/28 15:52:50]

Shouldn't this be 'continue'?

[keishi, 2016/02/29 06:02:33]

Done.

                 node->tracePersistentNode(visitor);
                 ++persistentCount;
             }
@@ -98,6 +100,17 @@ public:
 };
 }
 
+bool CrossThreadPersistentRegion::shouldTracePersistentNode(Visitor* visitor, PersistentNode* node)
+{

[haraken, 2016/01/28 15:52:50]

Add ASSERT(!node->isUnused()).

[keishi, 2016/02/29 06:02:33]

Done.

+    CrossThreadPersistent<GCObject>* persistent = reinterpret_cast<CrossThreadPersistent<GCObject>*>(node->self());
+    ASSERT(persistent);
+    Address rawObject = reinterpret_cast<Address>(persistent->get());
+    // TODO: Why do we need to return true?

[haraken, 2016/01/28 15:52:50]

I wonder why as well :) This should return false.

Maybe is this related to the above mistake between return and continue?

[keishi, 2016/02/29 06:02:33]

Thanks, looks like it was.

+    if (!rawObject)
+        return true;
+    return visitor->gcData()->threadState()->gcGroup()->threads().contains(ThreadState::forObject(rawObject));

[haraken, 2016/01/28 15:52:50]

forObject => fromAddress (for consistency with HeapPage's methods)

[keishi, 2016/02/29 06:02:33]

Done.

+}
+
 void CrossThreadPersistentRegion::prepareForThreadStateTermination(ThreadState* threadState)
 {
     // For heaps belonging to a thread that's detaching, any cross-thread persistents