Oilpan: disable conservative GCs during initial GC mixin construction.

Source/platform/heap/ThreadState.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 536 matching lines @@
     void shouldFlushHeapDoesNotContainCache() { m_shouldFlushHeapDoesNotContainCache = true; }
 
     void registerTraceDOMWrappers(v8::Isolate* isolate, void (*traceDOMWrappers)(v8::Isolate*, Visitor*))
     {
         m_isolate = isolate;
         m_traceDOMWrappers = traceDOMWrappers;
     }
 
     double collectionRate() const { return m_collectionRate; }
 
+    // By entering a gc-forbidden scope, conservative GCs will not
+    // be allowed while handling an out-of-line allocation request.
+    // Intended used when constructing subclasses of GC mixins, where
+    // the object being constructed cannot be safely traced & marked
+    // fully should a GC be allowed while its subclasses are being
+    // constructed.
+    void enterGCForbiddenScope(unsigned delta)
+    {
+        m_gcForbiddenCount += delta;
+    }
+
+#if ENABLE(ASSERT)
+    bool isGCForbidden() const { return m_gcForbiddenCount; }
+#endif
+
 private:
     ThreadState();
     ~ThreadState();
 
     void enterSafePoint(StackState, void*);
     NO_SANITIZE_ADDRESS void copyStackUntilSafePointScope();
     void clearSafePointScopeMarker()
     {
         m_safePointStackCopy.clear();
         m_safePointScopeMarker = nullptr;
@@ skipping 21 matching lines @@
     void cleanup();
     void cleanupPages();
 
     void unregisterPreFinalizerInternal(void*);
     void invokePreFinalizers(Visitor&);
 
 #if ENABLE(GC_PROFILING)
     void snapshotFreeList();
 #endif
 
-    // By entering a gc-forbidden scope, conservative GCs will not
-    // be allowed while handling an out-of-line allocation request.
-    // Intended used when constructing subclasses of GC mixins, where
-    // the object being constructed cannot be safely traced & marked
-    // fully should a GC be allowed while its subclasses are being
-    // constructed.
-    template<typename U, typename V> friend class AllocateObjectTrait;
-    void enterGCForbiddenScope() { m_gcForbiddenCount++; }
+    template<typename U> friend class GarbageCollectedMixinConstructorMarker;
     void leaveGCForbiddenScope()
     {
         ASSERT(m_gcForbiddenCount > 0);
         m_gcForbiddenCount--;
     }
 
     friend class SafePointAwareMutexLocker;
     friend class SafePointBarrier;
     friend class SafePointScope;
 
@@ skipping 64 matching lines @@
 };
 
 template<> class ThreadStateFor<AnyThread> {
 public:
     static ThreadState* state() { return ThreadState::current(); }
 };
 
 } // namespace blink
 
 #endif // ThreadState_h