It is present in the features.gypi but not in the BUILD.gn.
atom/browser/api/atom_api_view.cc
v8::Local<v8::FunctionTemplate> prototype) {
  prototype->SetClassName(mate::StringToV8(isolate, "View"));
#if defined(ENABLE_VIEW_API)
  mate::ObjectTemplateBuilder(isolate, prototype->PrototypeTemplate())
      .SetMethod("setLayoutManager", &View::SetLayoutManager)
      .SetMethod("addChildView", &View::AddChildView)
      .SetMethod("addChildViewAt", &View::AddChildViewAt);
#endif
}
}  
}  
namespace {
using atom::api::View;
void Initialize(v8::Local<v8::Object> exports,
                v8::Local<v8::Value> unused,
                v8::Local<v8::Context> context,
                void* priv) {
  v8::Isolate* isolate = context->GetIsolate();
  View::SetConstructor(isolate, base::Bind(&View::New));
  mate::Dictionary constructor(isolate,
                               View::GetConstructor(isolate)->GetFunction());
  mate::Dictionary dict(isolate, exports);
  dict.Set("View", constructor);
}
}  
NODE_BUILTIN_MODULE_CONTEXT_AWARE(atom_browser_view, Initialize)