[tracing] Adding class-wise memory statistics to blink gc memory dumps

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 60cca5cd57156ff459003a7945c3c9fef89c6f21..71c98d9389d20d75a9442bb51c01eefeb3a1d47c 100644
--- a/Source/platform/heap/Visitor.h
+++ b/Source/platform/heap/Visitor.h
@@ -42,10 +42,8 @@
 #include "wtf/HashMap.h"
 #include "wtf/HashTraits.h"
 #include "wtf/TypeTraits.h"
-#if ENABLE(GC_PROFILING)
 #include "wtf/InstanceCounter.h"
 #include "wtf/text/WTFString.h"
-#endif
 
 namespace blink {
 
@@ -396,12 +394,30 @@ public:
 
     inline MarkingMode markingMode() const { return m_markingMode; }
 
+    void setHostInfo(void* object, const String& name)
+    {
+        m_hostObject = object;
+        m_hostName = name;
+    }
+
+    inline bool isGlobalMarkingVisitor() const { return m_isGlobalMarkingVisitor; }
+
 protected:
     explicit Visitor(MarkingMode markingMode)
         : m_markingMode(markingMode)
     { }
 
     virtual void registerWeakCellWithCallback(void**, WeakCallback) = 0;
+#if ENABLE(GC_PROFILING)
+    virtual void recordObjectGraphEdge(const void*) = 0;
+#endif
+
+    void* m_hostObject;
+    String m_hostName;
+
+#if ENABLE(ASSERT)
+    virtual void checkMarkingAllowed() { }
+#endif
 
 private:
     static Visitor* fromHelper(VisitorHelper<Visitor>* helper) { return static_cast<Visitor*>(helper); }
@@ -411,6 +427,16 @@ private:
 };
 
 #if ENABLE(GC_PROFILING)
+template <typename Derived>
+template <typename T>
+void VisitorHelper<Derived>::handleWeakCell(Visitor* self, void* obj)
+{
+    T** cell = reinterpret_cast<T**>(obj);
+    if (*cell && !self->isHeapObjectAlive(*cell))
+        *cell = nullptr;
+}
+#endif
+
 template<typename T>
 struct TypenameStringTrait {
     static const String& get()
@@ -419,7 +445,6 @@ struct TypenameStringTrait {
         return typenameString;
     }
 };
-#endif
 
 } // namespace blink