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 fcb060ca55e80643beaec9ba133fc81e5b72332e..896c0658130f276299b0b4d6623ea6d600d34e0c 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, ShouldTraceCallback shouldTrace)
 {
     m_freeListHead = nullptr;
     int persistentCount = 0;
@@ -68,6 +68,8 @@ void PersistentRegion::tracePersistentNodes(Visitor* visitor)
                 freeListNext = node;
                 ++freeCount;
             } else {
+                if (shouldTrace && !shouldTrace(visitor, node))

[haraken, 2016/02/29 11:17:45]

Nit: Or you can implement PersistentRegion::shouldTracePersistentNode, which
unconditionally returns true. Then you won't need to check if shouldTrace is
nullptr or not.

[keishi, 2016/03/02 06:01:03]

Done.

+                    continue;
                 node->tracePersistentNode(visitor);
                 ++persistentCount;
             }
@@ -88,7 +90,6 @@ void PersistentRegion::tracePersistentNodes(Visitor* visitor)
             slots = slots->m_next;
         }
     }
-    ASSERT(persistentCount == m_persistentCount);

[haraken, 2016/02/29 11:17:45]

Can we keep this assert by incrementing persistentCount before the line 72?

[keishi, 2016/03/02 06:01:03]

Done.

 }
 
 namespace {
@@ -98,6 +99,16 @@ public:
 };
 }
 
+bool CrossThreadPersistentRegion::shouldTracePersistentNode(Visitor* visitor, PersistentNode* node)
+{
+    CrossThreadPersistent<GCObject>* persistent = reinterpret_cast<CrossThreadPersistent<GCObject>*>(node->self());
+    ASSERT(persistent);
+    Address rawObject = reinterpret_cast<Address>(persistent->get());
+    if (!rawObject)
+        return false;
+    return visitor->visitorScope()->heap().threads().contains(ThreadState::fromObject(rawObject));
+}
+
 void CrossThreadPersistentRegion::prepareForThreadStateTermination(ThreadState* threadState)
 {
     // For heaps belonging to a thread that's detaching, any cross-thread persistents
@@ -126,7 +137,7 @@ void CrossThreadPersistentRegion::prepareForThreadStateTermination(ThreadState*
             // but not invalidate its CrossThreadPersistent<>s.
             if (page->orphaned())
                 continue;
-            if (page->heap()->threadState() == threadState)
+            if (page->arena()->threadState() == threadState)
                 persistent->clear();
         }
         slots = slots->m_next;