UnityPlayerNativeActivity vs GoogleUnityActivity

I have google cardboard sdk and my web view plugin which renders web page on texture, When my web view appears. all my 2d buttons and screen touch stopped working.

even after closing webview also my 2d buttons did not work.

I observed in manifest, two activity one is UnityPlayerNativeActivity and second is GoogleUnityActivity.

When i place the launcher in GoogleUnityActivity my app runs but 2d button and touch did not work.
When i place the launcher in UnityPlayerNativeActivity my app runs and 2d buttons works but i get error like can not cast from UnityPlayerNativeActivity to GoogleUnityActivity.

Why UnityPlayerNativeActivity conflicts with GoogleUnityActivity?

What build of Unity are you using with this project?

I am using unity 5.3.0f4