code: function() {
          if (this._transitionElement) {
              for (var i=this.transitionendEvents.length-1; i>=0; --i) {
                  OpenLayers.Event.stopObserving(this._transitionElement,
                      this.transitionendEvents[i], this._removeBackBuffer);
              }
              delete this._transitionElement;
          }
          if(this.backBuffer) {
              if (this.backBuffer.parentNode) {
                  this.backBuffer.parentNode.removeChild(this.backBuffer);
              }
              this.backBuffer = null;
              this.backBufferResolution = null;
              if(this.backBufferTimerId !== null) {
                  window.clearTimeout(this.backBufferTimerId);
                  this.backBufferTimerId = null;
              }
          }
      }
docs: Method: removeBackBuffer
  Remove back buffer from DOM.