Replaced GLFW with native emscripten WebGL init, to be able to set PreserveDrawingBuffer attribute, which is needed for mirroring to work on Firefox.
Replaced GLFW with native emscripten WebGL init, to be able to set PreserveDrawingBuffer attribute, which is needed for mirroring to work on Firefox.

llatta/WebAssembly-WebVR-HelloWorld,llatta/WebAssembly-WebVR-HelloWorld