This is a polyfill for the WebGL extension OES_texture_float_linear. Try the live demo to see if the polyfill works for your browser.
OES_texture_float_linear was created to fix a mistake in the implementation of OES_texture_float. Although the spec for OES_texture_float requires that floating-point textures with linear filtering be marked as incomplete, the implementation of OES_texture_float in both Chrome and Firefox allowed linear filtering on floating-point textures. This caused apps that used linear filtering and floating-point textures to break on some mobile platforms that support floating-point textures but not linear filtering.
Upcoming browsers will prevent an app from using linear filtering on floating-point textures unless the app successfully acquires the OES_texture_float_linear extension. However, apps that check for OES_texture_float_linear support will then stop working on current browsers that don't know about OES_texture_float_linear. This polyfill checks if linear filtering works even though OES_texture_float_linear isn't supported.
<script src="OES_texture_float_linear-polyfill.js"></script>
<script>
var gl = document.createElement('canvas').getContext('experimental-webgl');
document.write('OES_texture_float_linear: ' + !!gl.getExtension('OES_texture_float_linear'));
</script>