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

Source/heap/Visitor.h

Index: Source/heap/Visitor.h
diff --git a/Source/heap/Visitor.h b/Source/heap/Visitor.h
index 06c4c1ac5fb2e652479cdfeeceafaf5c46e3cc56..a3d26097405ef78287b07b56c1c7a39addf755d2 100644
--- a/Source/heap/Visitor.h
+++ b/Source/heap/Visitor.h
@@ -39,6 +39,7 @@
 namespace WebCore {
 
 template<typename T> class Member;
+template<typename T> class Result;
 
 #ifndef NDEBUG
 #define DECLARE_GC_TYPE_MARKER         \
@@ -118,6 +119,18 @@ public:
         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)
     {