Oilpan: Reduce sizeof(Persistent) to 16 byte

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 34 matching lines @@
 #include "wtf/text/WTFString.h"
 
 namespace v8 {
 class Isolate;
 };
 
 namespace blink {
 
 class BasePage;
 class CallbackStack;
+class CrossThreadPersistentRegion;
 struct GCInfo;
 class GarbageCollectedMixinConstructorMarker;
 class HeapObjectHeader;
 class PageMemoryRegion;
 class PageMemory;
-class PersistentAnchor;
+class PersistentRegion;
 class BaseHeap;
 class SafePointAwareMutexLocker;
 class SafePointBarrier;
 class ThreadState;
 class Visitor;
 
 using Address = uint8_t*;
 
 using FinalizationCallback = void (*)(void*);
 using VisitorCallback = void (*)(Visitor*, void* self);
@@ skipping 394 matching lines @@
     }
 
 #if ENABLE(ASSERT) || ENABLE(GC_PROFILING)
     // Infrastructure to determine if an address is within one of the
     // address ranges for the Blink heap. If the address is in the Blink
     // heap the containing heap page is returned.
     BasePage* findPageFromAddress(Address);
     BasePage* findPageFromAddress(const void* pointer) { return findPageFromAddress(reinterpret_cast<Address>(const_cast<void*>(pointer))); }
 #endif
 
-    // List of persistent roots allocated on the given thread.
-    PersistentAnchor* roots() const { return m_persistents.get(); }
+    // A region of PersistentNodes allocated on the given thread.
+    PersistentRegion* persistentRegion() const { return m_persistentRegion.get(); }
 
-    // List of global persistent roots not owned by any particular thread.
-    // globalRootsMutex must be acquired before any modifications.
-    static PersistentAnchor& globalRoots();
-    static Mutex& globalRootsMutex();
+    // A region of PersistentNodes not owned by any particular thread.
+    static CrossThreadPersistentRegion& crossThreadPersistentRegion();
 
     // Visit local thread stack and trace all pointers conservatively.
     void visitStack(Visitor*);
 
     // Visit the asan fake stack frame corresponding to a slot on the
     // real machine stack if there is one.
     void visitAsanFakeStackForPointer(Visitor*, Address);
 
     // Visit all persistents allocated on this thread.
     void visitPersistents(Visitor*);
@@ skipping 234 matching lines @@
     // We can't create a static member of type ThreadState here
     // because it will introduce global constructor and destructor.
     // We would like to manage lifetime of the ThreadState attached
     // to the main thread explicitly instead and still use normal
     // constructor and destructor for the ThreadState class.
     // For this we reserve static storage for the main ThreadState
     // and lazily construct ThreadState in it using placement new.
     static uint8_t s_mainThreadStateStorage[];
 
     ThreadIdentifier m_thread;
-    OwnPtr<PersistentAnchor> m_persistents;
+    OwnPtr<PersistentRegion> m_persistentRegion;
     StackState m_stackState;
     intptr_t* m_startOfStack;
     intptr_t* m_endOfStack;
     void* m_safePointScopeMarker;
     Vector<Address> m_safePointStackCopy;
     bool m_atSafePoint;
     Vector<Interruptor*> m_interruptors;
     bool m_sweepForbidden;
     size_t m_noAllocationCount;
     size_t m_gcForbiddenCount;
@@ skipping 46 matching lines @@
 };
 
 template<> class ThreadStateFor<AnyThread> {
 public:
     static ThreadState* state() { return ThreadState::current(); }
 };
 
 } // namespace blink
 
 #endif // ThreadState_h