[oilpan] Fix iterators over member collections to return Result<T>

Source/heap/Visitor.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 21 matching lines @@
 #define Visitor_h
 
 #include <wtf/Deque.h>
 #include <wtf/Forward.h>
 #include <wtf/HashTraits.h>
 #include <wtf/HashSet.h>
 
 namespace WebCore {
 
 template<typename T> class Member;
+template<typename T> class Result;
 
 #ifndef NDEBUG
 #define DECLARE_GC_TYPE_MARKER         \
 public:                                \
     static const char* s_gcTypeMarker; \
 private:                               \
 
 #define DEFINE_GC_TYPE_MARKER(type) const char* type::s_gcTypeMarker = #type
 #else
 #define DECLARE_GC_TYPE_MARKER
@@ skipping 59 matching lines @@
     void visit(const Member<T>& t)
     {
         if (!t)
             return;
 #ifndef NDEBUG
         AcceptTrait<T>::check(this, t.raw());
 #endif
         AcceptTrait<T>::visit(this, t.raw());
     }
 
+    // Result version of the one-argument templated visit method.

[Mads Ager (chromium), 2013/08/16 10:23:41]

Could you expand the comment here to state why this is needed. You steal the
pointer from the Result here and we normally do not want to visit any Results at
all.

[Erik Corry, 2013/08/16 11:39:27]

Done.

+    template<typename T>
+    void visit(const Result<T>& t)
+    {
+        if (!t)
+            return;
+#ifndef NDEBUG
+        AcceptTrait<T>::check(this, t.releaseRaw());
+#endif
+        AcceptTrait<T>::visit(this, t.releaseRaw());
+    }
+
     template<typename T, size_t N>
     void visit(const Vector<Member<T>, N>& vector)
     {
         for (typename Vector<Member<T>, N>::const_iterator it = vector.begin(); it != vector.end(); ++it)
             visit(*it);
     }
 
     template<typename T>
     void visit(const HashSet<Member<T> >& hashSet)
     {
@@ skipping 151 matching lines @@
 public:
     virtual void accept(Visitor*) = 0;
     virtual ~HeapVisitable()
     {
     }
 };
 
 }
 
 #endif