[oilpan] Resurrect a loop-back persistent handle in RefCountedHeapAllocated

Source/wtf/RefCounted.h

Index: Source/wtf/RefCounted.h
diff --git a/Source/wtf/RefCounted.h b/Source/wtf/RefCounted.h
index 0504b9ed2818d7ad9fd164fd9c5a256ab6036c9e..d7214a964fc97071f10aae3636cb248756858c30 100644
--- a/Source/wtf/RefCounted.h
+++ b/Source/wtf/RefCounted.h
@@ -33,7 +33,13 @@ namespace WTF {
 #ifdef NDEBUG
 #define CHECK_REF_COUNTED_LIFECYCLE 0
 #else
-#define CHECK_REF_COUNTED_LIFECYCLE 1
+// FIXME(oilpan): Enable this check once we replace all
+// RefCountedHeapAllocated with HeapAllocated.
+// We have to disable the check for RefCountedHeapAllocated
+// since we have to allow the following situation in RefCountedHeapAllocated.
+// (1) A reference count becomes 0, but Handles keep references to the object.
+// (2) The Handle is assigned to a RefPtr. The reference count becomes 1.
+#define CHECK_REF_COUNTED_LIFECYCLE 0
 #endif
 
 // This base class holds the non-template methods and attributes.
@@ -41,27 +47,6 @@ namespace WTF {
 // generated by the compiler (technique called template hoisting).
 class RefCountedBase {
 public:
-    void ref()
-    {
-#if CHECK_REF_COUNTED_LIFECYCLE
-        // Start thread verification as soon as the ref count gets to 2. This
-        // heuristic reflects the fact that items are often created on one thread
-        // and then given to another thread to be used.
-        // FIXME: Make this restriction tigher. Especially as we move to more
-        // common methods for sharing items across threads like CrossThreadCopier.h
-        // We should be able to add a "detachFromThread" method to make this explicit.
-        if (m_refCount == 1)
-            m_verifier.setShared(true);
-        // If this assert fires, it either indicates a thread safety issue or
-        // that the verification needs to change. See ThreadRestrictionVerifier for
-        // the different modes.
-        ASSERT(m_verifier.isSafeToUse());
-        ASSERT(!m_deletionHasBegun);
-        ASSERT(!m_adoptionIsRequired);
-#endif
-        ++m_refCount;
-    }
-
     bool hasOneRef() const
     {
 #if CHECK_REF_COUNTED_LIFECYCLE
@@ -135,6 +120,27 @@ protected:
 #endif
     }
 
+    void refBase()
+    {
+#if CHECK_REF_COUNTED_LIFECYCLE
+        // Start thread verification as soon as the ref count gets to 2. This
+        // heuristic reflects the fact that items are often created on one thread
+        // and then given to another thread to be used.
+        // FIXME: Make this restriction tigher. Especially as we move to more
+        // common methods for sharing items across threads like CrossThreadCopier.h
+        // We should be able to add a "detachFromThread" method to make this explicit.
+        if (m_refCount == 1)
+            m_verifier.setShared(true);
+        // If this assert fires, it either indicates a thread safety issue or
+        // that the verification needs to change. See ThreadRestrictionVerifier for
+        // the different modes.
+        ASSERT(m_verifier.isSafeToUse());
+        ASSERT(!m_deletionHasBegun);
+        ASSERT(!m_adoptionIsRequired);
+#endif
+        ++m_refCount;
+    }
+
     // Returns whether the pointer should be freed or not.
     bool derefBase()
     {
@@ -149,6 +155,7 @@ protected:
 #if CHECK_REF_COUNTED_LIFECYCLE
             m_deletionHasBegun = true;
 #endif
+            --m_refCount;

[haraken, 2013/05/29 14:53:45]

This is critical :)

[Mads Ager (chromium), 2013/05/29 16:46:38]

Yeah, I see, otherwise the ref will actually never reach zero. :-)

             return true;
         }
 
@@ -196,6 +203,11 @@ inline void adopted(RefCountedBase* object)
 template<typename T> class RefCounted : public RefCountedBase {
     WTF_MAKE_NONCOPYABLE(RefCounted); WTF_MAKE_FAST_ALLOCATED;
 public:
+    void ref()
+    {
+        refBase();
+    }
+
     void deref()
     {
         if (derefBase())
@@ -213,6 +225,11 @@ template<typename T> class RefCountedCustomAllocated : public RefCountedBase {
     WTF_MAKE_NONCOPYABLE(RefCountedCustomAllocated);
 
 public:
+    void ref()
+    {
+        refBase();
+    }
+
     void deref()
     {
         if (derefBase())