function rectContains(rect1, rect2) {
  return rect2.top >= rect1.top &&
    rect2.right <= rect1.right &&
    rect2.bottom <= rect1.bottom &&
    rect2.left >= rect1.left;
}
Returns whether rect2 is contained entirely within rect1;
@param {LH.Artifacts.Rect} rect1
@param {LH.Artifacts.Rect} rect2
@return {boolean}