According to a Mozilla report, the Samsung Internet for GearVR browser will support WebGL natively. This is based on the open source chromium engine version (M44) which is the same that is seen on the mobile Samsung Internet for Android mobile browser.

It will let you browse through the virtual reality experiences that are found on the web. You will get an immersive experience provided you visit a site which has supporting content.

This effectively means that you get to see content beyond the OculusVR store or that provided by Samsung. You will have to enable WebVR within your internet for GearVR browser for this feature to work.