function CacheManager() {
      _classCallCheck(this, CacheManager);

      // never clear cached geometries
      this.geometries = [];
      this.clear();
    }
Here we create a CacheManager class object
   This will store geometries attributes arrays, textures and WebGL programs in arrays
   This helps speed up slow synchronous CPU operations such as WebGL shaders compilations, images decoding, etc.
     returns :
   @this: our CacheManager class object
*