Support merged Dart-JS callstacks

Source/bindings/dart/DartUtilities.h

Index: Source/bindings/dart/DartUtilities.h
diff --git a/Source/bindings/dart/DartUtilities.h b/Source/bindings/dart/DartUtilities.h
index 5e728715d0581f43b1e097dc99ee7fe4144d14ef..67ca96dbcc12d172c9dd344c0511b8d12ba8179f 100644
--- a/Source/bindings/dart/DartUtilities.h
+++ b/Source/bindings/dart/DartUtilities.h
@@ -237,7 +237,7 @@ public:
     static PassRefPtr<ScriptCallStack> createScriptCallStack();
     static ScriptCallFrame getTopFrame(Dart_StackTrace, Dart_Handle& exception);
     static ScriptCallFrame toScriptCallFrame(Dart_ActivationFrame, Dart_Handle& exception);
-
+    static size_t currentStackDepth();
     static const uint8_t* fullSnapshot(LocalFrame*);
 
     static Dart_Handle canonicalizeUrl(Dart_Handle library, Dart_Handle urlHandle, String url);
@@ -885,6 +885,8 @@ public:
     V8Scope(DartDOMData*);
     ~V8Scope();
 private:
+    void incrementRecursionLevel();
+
     v8::Isolate* m_v8Isolate;
     DartDOMData* m_dartDOMData;
     v8::HandleScope m_handleScope;