function createTransformFeedbackInfo(gl, program) {
  var info = {};
  var numVaryings = gl.getProgramParameter(program, TRANSFORM_FEEDBACK_VARYINGS);

  for (var ii = 0; ii < numVaryings; ++ii) {
    var varying = gl.getTransformFeedbackVarying(program, ii);
    info[varying.name] = {
      index: ii,
      type: varying.type,
      size: varying.size
    };
  }

  return info;
}
Create TransformFeedbackInfo for passing to bindTransformFeedbackInfo.
@param {WebGLRenderingContext} gl The WebGLRenderingContext to use.
@param {WebGLProgram} program an existing WebGLProgram.
@return {Object<string, module:twgl.TransformFeedbackInfo>}
@memberOf module:twgl