Move TestRunner from CppVariable to gin::Wrappable

gin/arguments.h

Index: gin/arguments.h
diff --git a/gin/arguments.h b/gin/arguments.h
index ec4ae80e88219d5fcb15ecb770bfdf429c672849..509c22ca14f892f3188348e6b1b9fae01b5caafa 100644
--- a/gin/arguments.h
+++ b/gin/arguments.h
@@ -56,6 +56,17 @@ class GIN_EXPORT Arguments {
     return true;
   }
 
+  bool Skip() {
+    if (next_ >= info_->Length())
+      return false;
+    next_++;
+    return true;
+  }
+
+  int Length() const {
+    return info_->Length();
+  }
+
   template<typename T>
   void Return(T val) {
     info_->GetReturnValue().Set(ConvertToV8(isolate_, val));