code: function (renderer) {
  
          var cache = this._cache;
  
          cache.use(renderer.__uid__);
          var chunks = cache.get('chunks');
          if (chunks) {
              for (var c = 0; c < chunks.length; c++) {
                  var chunk = chunks[c];
  
                  for (var k = 0; k < chunk.attributeBuffers.length; k++) {
                      var attribs = chunk.attributeBuffers[k];
                      renderer.gl.deleteBuffer(attribs.buffer);
                  }
  
                  if (chunk.indicesBuffer) {
                      renderer.gl.deleteBuffer(chunk.indicesBuffer.buffer);
                  }
              }
          }
          if (this.__vaoCache) {
              var vaoExt = renderer.getGLExtension('OES_vertex_array_object');
              for (var id in this.__vaoCache) {
                  var vao = this.__vaoCache[id].vao;
                  if (vao) {
                      vaoExt.deleteVertexArrayOES(vao);
                  }
              }
          }
          this.__vaoCache = {};
          cache.deleteContext(renderer.__uid__);
      }
docs: Dispose geometry data in GL context.
  @param {clay.Renderer} renderer