For easy integration of IFrame application (WebGL) with VK user interface you can use VkSDK for Unity.
Asset works without additional WebGL template and without deprecated ExternalEval/ExternalCall. Used only .jslib/.jspre extensions.
Features Supported:
- Open the following windows: application installation, settings, friend invitation and vote input to pay for services.
- Receive events about successful installation of the application by the user, change of settings and balance of the user inside the application.
- Access API server methods.
DEMO: https://vk.com/app6277370
Unity Asset Store URL: https://www.assetstore.unity3d.com/#!/content/107054