Oilpan: Introduce WeakProcessingVisitor

Source/platform/heap/Visitor.h

Index: Source/platform/heap/Visitor.h
diff --git a/Source/platform/heap/Visitor.h b/Source/platform/heap/Visitor.h
index 9400ee248c8245ae7a48f503adba4ee8b6b25bf4..f52b9a3e0271aef936583b25638687dcd7a1885a 100644
--- a/Source/platform/heap/Visitor.h
+++ b/Source/platform/heap/Visitor.h
@@ -330,6 +330,7 @@ public:
     enum MarkingMode {
         GlobalMarking,
         ThreadLocalMarking,
+        WeakProcessing,
     };
 
     virtual ~Visitor() { }
@@ -392,11 +393,11 @@ public:
     }
 #endif
 
-    inline bool isGlobalMarkingVisitor() const { return m_isGlobalMarkingVisitor; }
+    inline MarkingMode markingMode() const { return m_markingMode; }
 
 protected:
     explicit Visitor(MarkingMode markingMode)
-        : m_isGlobalMarkingVisitor(markingMode == GlobalMarking)
+        : m_markingMode(markingMode)
     { }
 
     virtual void registerWeakCellWithCallback(void**, WeakCallback) = 0;
@@ -414,6 +415,7 @@ protected:
 private:
     static Visitor* fromHelper(VisitorHelper<Visitor>* helper) { return static_cast<Visitor*>(helper); }
 
+    const MarkingMode m_markingMode;
     bool m_isGlobalMarkingVisitor;
 };