two pass phantom collection

src/debug.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_DEBUG_H_
 #define V8_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 243 matching lines @@
 
   Isolate* isolate_;
 };
 
 
 // Linked list holding debug info objects. The debug info objects are kept as
 // weak handles to avoid a debug info object to keep a function alive.
 class DebugInfoListNode {
  public:
   explicit DebugInfoListNode(DebugInfo* debug_info);
-  virtual ~DebugInfoListNode();
+  virtual ~DebugInfoListNode() { ClearInfo(); }
 
   DebugInfoListNode* next() { return next_; }
   void set_next(DebugInfoListNode* next) { next_ = next; }
-  Handle<DebugInfo> debug_info() { return debug_info_; }
+  Handle<DebugInfo> debug_info() { return Handle<DebugInfo>(debug_info_); }
+
+  void ClearInfo();
 
  private:
   // Global (weak) handle to the debug info object.
-  Handle<DebugInfo> debug_info_;
+  DebugInfo** debug_info_;
 
   // Next pointer for linked list.
   DebugInfoListNode* next_;
 };
 
 
 
 // Message delivered to the message handler callback. This is either a debugger
 // event or the response to a command.
 class MessageImpl: public v8::Debug::Message {
@@ skipping 557 matching lines @@
   // several frames above.
   // There is no calling conventions here, because it never actually gets
   // called, it only gets returned to.
   static void GenerateFrameDropperLiveEdit(MacroAssembler* masm);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_DEBUG_H_